Loopbacks are used for a variety of purposes: some well understood, others “just because.” Let’s look at a few.
First and foremost, a loopback is a virtual interface on a router that really doesn’t go “down.” There’s no such thing as a physical circuit failure for something for which there is no physical presence. So, this makes loopback interfaces quite reliable.
Loopbacks are used for management interfaces. It’s good to have a separate set of network addresses spread throughout the network to manage things. Various strategically placed access lists can also help make sure that only appropriate personnel/locations can access these loopback addresses. You can also use this as the source address for locally generated traffic, which provides some stability to the network and consistency in the ACL generation.
Management interfaces really only need to have a /32 route (host-specific) for management. Logically, how many management things does it take to talk to the same device? One is plenty. This also conserves IP addresses in case the 16.7 million or so in the 10.x.x.x range weren’t enough for you.
Beyond that, loopback interfaces are often used to indicate router IDs for routing protocols such as BGP or OSPF. It’s a good to have a known IP address that must be unique in the network to keep some semblance of sanity within the routing protocols. The router IDs between routing protocols should match.
Inside a routing protocol, like OSPF, router IDs are used specifically for setting up OSPF Virtual Links. You can also “hard code” a router ID with the “router-id” command within the routing process. These router IDs are again a single IP address, so using a /32 would be perfectly acceptable.
Next, we get into pools of addresses. Think about the “ip local pool” command. This can be used in reference to dial-in users or Virtual Private Dial Network (VPDN) users within PPPoE, PPPoA or just plain dial-up PPP connections. Or the “ip nat pool” command used to set a pool of addresses for Virtual Private Network (IPSec VPN or PPTP VPN) users in terminating their connection.
Whenever a user establishes a connection to the router, they are assigned a “local” address from one of these pools. They use this assigned address to communicate with the rest of the network. Makes sense so far, right?
Well, in the IP world we rely on routes. The router that has these pools to assign, we certainly assume that it has routes to go places and therefore packets get sent. But then what? Always remember that routing works in both directions. Going to someplace and getting back from that someplace. So, if you obtain an address from a pool somewhere, it should stand to reason that other devices know how to get back to your pool.
That’s where routing protocols come into play. Routing protocols can’t advertise a network from a “pool:” that isn’t an interface, and only interfaces are allowed to be part of the routing process. So, we need to use an interface to hold the pool of addresses for us. And this is where loopback interfaces yet again help us out by holding these addresses. Here we would use something larger than a /32 subnet to accommodate all of the IP addresses that are assigned into pools.
We may have more than one pool and therefore more than one loopback address going on with a larger mask. So, like many things, the answer lies somewhere in the “it depends” world. But watch what you are using IP addresses for. Remember that routes work both ways and then ponder the idea why you may want to use multiple IP addresses and have some subnet masks larger than a host route.
Hope that helps!
Wednesday, February 24, 2010
What is natting
what is diffrance between NAT & PAT
NAT is Network address Translation ( ip address translate
from local ip to global ip and vice versa)
PAT is Port address translation ( port are translate from
local to global ip's ) like on port 8080 web service port
80 will work on PAT . it more over NAT only.
NAT is Network address Translation ( ip address translate
from local ip to global ip and vice versa)
PAT is Port address translation ( port are translate from
local to global ip's ) like on port 8080 web service port
80 will work on PAT . it more over NAT only.
Saturday, February 20, 2010
LAN Segmentation
This page will discuss the advantages of LAN segmentation and will describe LAN segmentation using bridges, switches, and routers. Also described will be the benefits of using each of these three internetworking devices.
Describe the advantages of LAN segmentation
When separate networks are needed or if a network has reached its physical limitations, segmentation is used. Segmenting a LAN can extend the network, reduce congestion, isolate network problems, and improve security.
Extending the network -- When the maximum physical limitations of a network has been reached, routers may be added to create new segments to allow additional hosts onto the LAN.
Reduce Congestion -- As the number of hosts on a single network increases, the bandwidth required also increases. By segmenting the LAN, you can reduce the number of hosts per network. If traffic consists of communications between hosts on the same segment, then bandwidth usage is substantially reduced.
Isolate network problems -- By dividing the network into smaller segments, you reduce the overflow of problems from one segment to the next. Hardware and software failures are some of the problems that can be reduced to affect smaller portions of the network.
Improve Security -- By utilizing segments, a network administrator can ensure that the internal structure of the network will not be visible from an outside source. Privileged packets will only be broadcast on the subnet it originated from, not throughout the network.
Describe LAN segmentation using bridges.
The term bridging refers to a technology in which a device (known as a bridge) connects two or more LAN segments. A bridge transmits datagrams from one segment to their destinations on other segments.
Bridges are capable of filtering frames based on any Layer 2 fields. A bridge, for example, can be programmed to reject (not forward) all frames sourced from a particular network. Because link-layer information often includes a reference to an upper-layer protocol, bridges usually can filter on this parameter. Furthermore, filters can be helpful in dealing with unnecessary broadcast and multicast packets. Because only a certain percentage of traffic is forwarded, a bridge or switch diminishes the traffic experienced by devices on all connected segments. The bridge or switch will act as a firewall for some potentially damaging network errors, and both accommodate communication between a larger number of devices than would be supported on any single LAN connected to the bridge.
Describe LAN segmentation using routers.
Because routers use Layer 3 addresses, which typically have structure, routers can use techniques (such as address summarization) to build networks that maintain performance and responsiveness as they grow in size. Segments are interconnected by routers to enable communication between LANs while blocking other types of traffic. Routers also allow for the interconnection of disparate LAN and WAN technologies while also implementing broadcast filters and logical firewalls. In general, if you need advanced internetworking services, such as broadcast firewalling and communication between dissimilar LANs, routers are necessary.
Describe LAN segmentation using switches.
Switches are data link layer devices that, like bridges, enable multiple physical LAN segments to be interconnected into a single larger network. Similar to bridges, switches forward and flood traffic based on MAC addresses. Because switching is performed in hardware instead of in software, however, it is significantly faster. Switches use either store-and-forward switching or cut-through switching when forwarding traffic.
Segmenting shared-media LANs divides the users into two or more separate LAN segments, reducing the number of users contending for bandwidth. LAN switching technology, which builds upon this trend, employs microsegmentation, which further segments the LAN to fewer users and ultimately to a single user with a dedicated LAN segment. Each switch port provides a dedicated, 10MB Ethernet segment. Segments are interconnected by internetworking devices that enable communication between LANs while blocking other types of traffic. Switches have the intelligence to monitor traffic and compile address tables, which then allows them to forward packets directly to specific ports in the LAN. Switches also usually provide nonblocking service, which allows multiple conversations (traffic between two ports) to occur simultaneously.
LAN switches can be used to segment networks into logically defined virtual workgroups (VLANs). This logical segmentation, commonly referred to as VLAN communication, offers a fundamental change in how LANs are designed, administered, and managed. Logical segmentation provides substantial benefits in LAN administration, security, and management of network broadcast across the enterprise.
Superior throughput performance, higher port density, lower per-port cost, and greater flexibility have contributed to the emergence of switches as replacement technology for bridges and as complements to routing technology.
Describe the benefits of network segmentation with bridges.
Transparent bridges successfully isolate intrasegment traffic, thereby reducing the traffic seen on each individual segment. This usually improves network response times, as seen by the user.
Bridges and switches extend the effective length of a LAN, permitting the attachment of distant stations that were not previously permitted.
Bridges can connect more than two LANs and use the Spanning Tree Algorithm to eliminate loops while still allowing connectivity and redundancy between them.
Bridges can compensate for speed discrepancies of WAN and LAN connections by using its buffering capabilities. This is done by storing the incoming data in on-board buffers and sending it over the serial link at a rate that the serial link can accommodate.
Some bridges are MAC-layer bridges, which bridge between homogeneous networks (for example, IEEE 802.3 and IEEE 802.3), while other bridges can translate between different link-layer protocols (for example, IEEE 802.3 and IEEE 802.5).
Describe the benefits of network segmentation with routers.
Routers offer the following benefits in LAN segmentation:
Media Transition--Routers are used to connect networks of different media types, taking care of the Layer 3 address translations and fragmentation requirements.
Broadcast control--By default, routers don't pass broadcasts and therefore restrict the broadcast domain. In addition to preventing broadcasts from radiating throughout the network, routers are also responsible for generating services to each LAN segment. The following are examples of services that the router provides to the network for a variety of protocols:
IP---Proxy ARP and Internet Control Message Protocol (ICMP)
IPX---SAP table updates
AppleTalk---ZIP table updates
Network management---SNMP queries
Packet Filtering--Routers can filter packets either inbound or outbound between LAN segments or LAN and WAN segments.
VLAN Communications--Routers remain vital for switched architectures configured as VLANs because they provide the communication between VLANs.
Large Packets--Routers can handle large packets by fragmenting them into smaller pieces, sending them across the network, and reassembling them whereas bridges discard frames that are too large.
Describe the benefits of network segmentation with switches.
Layer 2 switches offer some or all of the following benefits:
Unlike hubs and repeaters, switches allow multiple data streams to pass simultaneously.
LAN switches are used to interconnect multiple LAN segments. LAN switching provides dedicated, collision-free communication between network devices, with support for multiple simultaneous conversations.
Collisions--Switches reduce collisions on network segments because they provide dedicated bandwidth to each network segment and each connected segment is in a separate collision domain.
Bandwidth---LAN switches provide excellent performance for individual users by allocating dedicated bandwidth to each switch port (for example, each network segment). This technique is known as microsegmenting. An Ethernet LAN switch improves bandwidth by separating collision domains and selectively forwarding traffic to the appropriate segments.
Dedicated Bandwidth---Switches deliver dedicated bandwidth to users through high-density group switched and switched 10BaseT or 100BaseT Ethernet.
VLANs---LAN switches can group individual ports into logical switched workgroups called VLANs, thereby restricting the broadcast domain to designated VLAN member ports. VLANs are also known as switched domains and autonomous switching domains. Communication between VLANs requires a router.
BACK
Describe the advantages of LAN segmentation
When separate networks are needed or if a network has reached its physical limitations, segmentation is used. Segmenting a LAN can extend the network, reduce congestion, isolate network problems, and improve security.
Extending the network -- When the maximum physical limitations of a network has been reached, routers may be added to create new segments to allow additional hosts onto the LAN.
Reduce Congestion -- As the number of hosts on a single network increases, the bandwidth required also increases. By segmenting the LAN, you can reduce the number of hosts per network. If traffic consists of communications between hosts on the same segment, then bandwidth usage is substantially reduced.
Isolate network problems -- By dividing the network into smaller segments, you reduce the overflow of problems from one segment to the next. Hardware and software failures are some of the problems that can be reduced to affect smaller portions of the network.
Improve Security -- By utilizing segments, a network administrator can ensure that the internal structure of the network will not be visible from an outside source. Privileged packets will only be broadcast on the subnet it originated from, not throughout the network.
Describe LAN segmentation using bridges.
The term bridging refers to a technology in which a device (known as a bridge) connects two or more LAN segments. A bridge transmits datagrams from one segment to their destinations on other segments.
Bridges are capable of filtering frames based on any Layer 2 fields. A bridge, for example, can be programmed to reject (not forward) all frames sourced from a particular network. Because link-layer information often includes a reference to an upper-layer protocol, bridges usually can filter on this parameter. Furthermore, filters can be helpful in dealing with unnecessary broadcast and multicast packets. Because only a certain percentage of traffic is forwarded, a bridge or switch diminishes the traffic experienced by devices on all connected segments. The bridge or switch will act as a firewall for some potentially damaging network errors, and both accommodate communication between a larger number of devices than would be supported on any single LAN connected to the bridge.
Describe LAN segmentation using routers.
Because routers use Layer 3 addresses, which typically have structure, routers can use techniques (such as address summarization) to build networks that maintain performance and responsiveness as they grow in size. Segments are interconnected by routers to enable communication between LANs while blocking other types of traffic. Routers also allow for the interconnection of disparate LAN and WAN technologies while also implementing broadcast filters and logical firewalls. In general, if you need advanced internetworking services, such as broadcast firewalling and communication between dissimilar LANs, routers are necessary.
Describe LAN segmentation using switches.
Switches are data link layer devices that, like bridges, enable multiple physical LAN segments to be interconnected into a single larger network. Similar to bridges, switches forward and flood traffic based on MAC addresses. Because switching is performed in hardware instead of in software, however, it is significantly faster. Switches use either store-and-forward switching or cut-through switching when forwarding traffic.
Segmenting shared-media LANs divides the users into two or more separate LAN segments, reducing the number of users contending for bandwidth. LAN switching technology, which builds upon this trend, employs microsegmentation, which further segments the LAN to fewer users and ultimately to a single user with a dedicated LAN segment. Each switch port provides a dedicated, 10MB Ethernet segment. Segments are interconnected by internetworking devices that enable communication between LANs while blocking other types of traffic. Switches have the intelligence to monitor traffic and compile address tables, which then allows them to forward packets directly to specific ports in the LAN. Switches also usually provide nonblocking service, which allows multiple conversations (traffic between two ports) to occur simultaneously.
LAN switches can be used to segment networks into logically defined virtual workgroups (VLANs). This logical segmentation, commonly referred to as VLAN communication, offers a fundamental change in how LANs are designed, administered, and managed. Logical segmentation provides substantial benefits in LAN administration, security, and management of network broadcast across the enterprise.
Superior throughput performance, higher port density, lower per-port cost, and greater flexibility have contributed to the emergence of switches as replacement technology for bridges and as complements to routing technology.
Describe the benefits of network segmentation with bridges.
Transparent bridges successfully isolate intrasegment traffic, thereby reducing the traffic seen on each individual segment. This usually improves network response times, as seen by the user.
Bridges and switches extend the effective length of a LAN, permitting the attachment of distant stations that were not previously permitted.
Bridges can connect more than two LANs and use the Spanning Tree Algorithm to eliminate loops while still allowing connectivity and redundancy between them.
Bridges can compensate for speed discrepancies of WAN and LAN connections by using its buffering capabilities. This is done by storing the incoming data in on-board buffers and sending it over the serial link at a rate that the serial link can accommodate.
Some bridges are MAC-layer bridges, which bridge between homogeneous networks (for example, IEEE 802.3 and IEEE 802.3), while other bridges can translate between different link-layer protocols (for example, IEEE 802.3 and IEEE 802.5).
Describe the benefits of network segmentation with routers.
Routers offer the following benefits in LAN segmentation:
Media Transition--Routers are used to connect networks of different media types, taking care of the Layer 3 address translations and fragmentation requirements.
Broadcast control--By default, routers don't pass broadcasts and therefore restrict the broadcast domain. In addition to preventing broadcasts from radiating throughout the network, routers are also responsible for generating services to each LAN segment. The following are examples of services that the router provides to the network for a variety of protocols:
IP---Proxy ARP and Internet Control Message Protocol (ICMP)
IPX---SAP table updates
AppleTalk---ZIP table updates
Network management---SNMP queries
Packet Filtering--Routers can filter packets either inbound or outbound between LAN segments or LAN and WAN segments.
VLAN Communications--Routers remain vital for switched architectures configured as VLANs because they provide the communication between VLANs.
Large Packets--Routers can handle large packets by fragmenting them into smaller pieces, sending them across the network, and reassembling them whereas bridges discard frames that are too large.
Describe the benefits of network segmentation with switches.
Layer 2 switches offer some or all of the following benefits:
Unlike hubs and repeaters, switches allow multiple data streams to pass simultaneously.
LAN switches are used to interconnect multiple LAN segments. LAN switching provides dedicated, collision-free communication between network devices, with support for multiple simultaneous conversations.
Collisions--Switches reduce collisions on network segments because they provide dedicated bandwidth to each network segment and each connected segment is in a separate collision domain.
Bandwidth---LAN switches provide excellent performance for individual users by allocating dedicated bandwidth to each switch port (for example, each network segment). This technique is known as microsegmenting. An Ethernet LAN switch improves bandwidth by separating collision domains and selectively forwarding traffic to the appropriate segments.
Dedicated Bandwidth---Switches deliver dedicated bandwidth to users through high-density group switched and switched 10BaseT or 100BaseT Ethernet.
VLANs---LAN switches can group individual ports into logical switched workgroups called VLANs, thereby restricting the broadcast domain to designated VLAN member ports. VLANs are also known as switched domains and autonomous switching domains. Communication between VLANs requires a router.
BACK
LAN PROTOCOL
This page introduces the various media-access methods, transmission methods, topologies, and devices used in a local area network (LAN); to include methods and devices used in Ethernet/IEEE 802.3, Token Ring/IEEE 802.5, and Fiber Distributed Data Interface (FDDI).
A LAN is a high-speed, fault-tolerant data network that covers a relatively small geographic area. It typically connects workstations, personal computers, printers, and other devices. LANs offer computer users many advantages, including shared access to devices and applications, file exchange between connected users, and communication between users via electronic mail and other applications
Media-Access Methods
LAN protocols typically use one of two methods to access the physical network medium: carrier sense multiple access collision detect (CSMA/CD) and token passing.
In the CSMA/CD media-access scheme, network devices contend for use of the physical network medium. CSMA/CD is therefore sometimes called contention access. Examples of LANs that use the CSMA/CD media-access scheme are Ethernet/IEEE 802.3 networks, including 100BaseT.
In the token-passing media-access scheme, network devices access the physical medium based on possession of a token. Examples of LANs that use the token-passing media-access scheme are Token Ring/IEEE 802.5 and FDDI.
LAN Transmission Methods
LAN data transmissions fall into three classifications: unicast, multicast, and broadcast. In each type of transmission, a single packet is sent to one or more nodes.
In a unicast transmission, a single packet is sent from the source to a destination on a network.
A multicast transmission consists of a single data packet that is copied and sent to a specific subset of nodes on the network.
A broadcast transmission consists of a single data packet that is copied and sent to all nodes on the network.
LAN Topologies
LAN topologies define the manner in which network devices are organized. Four common LAN topologies exist: bus, ring, star, and tree. These topologies are logical architectures, but the actual devices need not be physically organized in these configurations. Logical bus and ring topologies, for example, are commonly organized physically as a star.
A bus topology is a linear LAN architecture in which transmissions from network stations propagate the length of the medium and are received by all other stations.
A ring topology is a LAN architecture that consists of a series of devices connected to one another by unidirectional transmission links to form a single closed loop. Both Token Ring/IEEE 802.5 and FDDI networks implement a ring topology.
A tree topology is a LAN architecture that is identical to the bus topology, except that branches with multiple nodes are possible in this case.
A star topology is a LAN architecture in which the endpoints on a network are connected to a common central hub, or switch, by dedicated links. Logical bus and ring topologies are often implemented physically in a star topology.
LAN Devices
Devices commonly used in LANs include repeaters, hubs, LAN extenders, bridges, LAN switches, and routers.
A repeater is a physical layer device used to interconnect the media segments of an extended network. A repeater essentially enables a series of cable segments to be treated as a single cable. Repeaters receive signals from one network segment and amplify, retime, and retransmit those signals to another network segment. These actions prevent signal deterioration caused by long cable lengths and large numbers of connected devices. Repeaters are incapable of performing complex filtering and other traffic processing. In addition, all electrical signals, including electrical disturbances and other errors, are repeated and amplified. The total number of repeaters and network segments that can be connected is limited due to timing and other issues.
A hub is a physical-layer device that connects multiple user stations, each via a dedicated cable. Electrical interconnections are established inside the hub. Hubs are used to create a physical star network while maintaining the logical bus or ring configuration of the LAN. In some respects, a hub functions as a multiport repeater.
A LAN extender is a remote-access multilayer switch that connects to a host router. LAN extenders forward traffic from all the standard network-layer protocols (such as IP, IPX, and AppleTalk), and filter traffic based on the MAC address or network-layer protocol type. LAN extenders scale well because the host router filters out unwanted broadcasts and multicasts. LAN extenders, however, are not capable of segmenting traffic or creating security firewalls.
Bridges analyze incoming frames, make forwarding decisions based on information contained in the frames, and forward the frames toward the destination. In some cases, such as source-route bridging, the entire path to the destination is contained in each frame. In other cases, such as transparent bridging, frames are forwarded one hop at a time toward the destination.
Switches are data link layer devices that, like bridges, enable multiple physical LAN segments to be interconnected into a single larger network. Similar to bridges, switches forward and flood traffic based on MAC addresses. Because switching is performed in hardware instead of in software, however, it is significantly faster. Switches use either store-and-forward switching or cut-through switching when forwarding traffic. Many types of switches exist, including ATM switches, LAN switches, and various types of WAN switches.
Routers perform two basic activities: determining optimal routing paths and transporting information groups (typically called packets) through an internetwork. In the context of the routing process, the latter of these is referred to as switching. Although switching is relatively straightforward, path determination can be very complex
A LAN is a high-speed, fault-tolerant data network that covers a relatively small geographic area. It typically connects workstations, personal computers, printers, and other devices. LANs offer computer users many advantages, including shared access to devices and applications, file exchange between connected users, and communication between users via electronic mail and other applications
Media-Access Methods
LAN protocols typically use one of two methods to access the physical network medium: carrier sense multiple access collision detect (CSMA/CD) and token passing.
In the CSMA/CD media-access scheme, network devices contend for use of the physical network medium. CSMA/CD is therefore sometimes called contention access. Examples of LANs that use the CSMA/CD media-access scheme are Ethernet/IEEE 802.3 networks, including 100BaseT.
In the token-passing media-access scheme, network devices access the physical medium based on possession of a token. Examples of LANs that use the token-passing media-access scheme are Token Ring/IEEE 802.5 and FDDI.
LAN Transmission Methods
LAN data transmissions fall into three classifications: unicast, multicast, and broadcast. In each type of transmission, a single packet is sent to one or more nodes.
In a unicast transmission, a single packet is sent from the source to a destination on a network.
A multicast transmission consists of a single data packet that is copied and sent to a specific subset of nodes on the network.
A broadcast transmission consists of a single data packet that is copied and sent to all nodes on the network.
LAN Topologies
LAN topologies define the manner in which network devices are organized. Four common LAN topologies exist: bus, ring, star, and tree. These topologies are logical architectures, but the actual devices need not be physically organized in these configurations. Logical bus and ring topologies, for example, are commonly organized physically as a star.
A bus topology is a linear LAN architecture in which transmissions from network stations propagate the length of the medium and are received by all other stations.
A ring topology is a LAN architecture that consists of a series of devices connected to one another by unidirectional transmission links to form a single closed loop. Both Token Ring/IEEE 802.5 and FDDI networks implement a ring topology.
A tree topology is a LAN architecture that is identical to the bus topology, except that branches with multiple nodes are possible in this case.
A star topology is a LAN architecture in which the endpoints on a network are connected to a common central hub, or switch, by dedicated links. Logical bus and ring topologies are often implemented physically in a star topology.
LAN Devices
Devices commonly used in LANs include repeaters, hubs, LAN extenders, bridges, LAN switches, and routers.
A repeater is a physical layer device used to interconnect the media segments of an extended network. A repeater essentially enables a series of cable segments to be treated as a single cable. Repeaters receive signals from one network segment and amplify, retime, and retransmit those signals to another network segment. These actions prevent signal deterioration caused by long cable lengths and large numbers of connected devices. Repeaters are incapable of performing complex filtering and other traffic processing. In addition, all electrical signals, including electrical disturbances and other errors, are repeated and amplified. The total number of repeaters and network segments that can be connected is limited due to timing and other issues.
A hub is a physical-layer device that connects multiple user stations, each via a dedicated cable. Electrical interconnections are established inside the hub. Hubs are used to create a physical star network while maintaining the logical bus or ring configuration of the LAN. In some respects, a hub functions as a multiport repeater.
A LAN extender is a remote-access multilayer switch that connects to a host router. LAN extenders forward traffic from all the standard network-layer protocols (such as IP, IPX, and AppleTalk), and filter traffic based on the MAC address or network-layer protocol type. LAN extenders scale well because the host router filters out unwanted broadcasts and multicasts. LAN extenders, however, are not capable of segmenting traffic or creating security firewalls.
Bridges analyze incoming frames, make forwarding decisions based on information contained in the frames, and forward the frames toward the destination. In some cases, such as source-route bridging, the entire path to the destination is contained in each frame. In other cases, such as transparent bridging, frames are forwarded one hop at a time toward the destination.
Switches are data link layer devices that, like bridges, enable multiple physical LAN segments to be interconnected into a single larger network. Similar to bridges, switches forward and flood traffic based on MAC addresses. Because switching is performed in hardware instead of in software, however, it is significantly faster. Switches use either store-and-forward switching or cut-through switching when forwarding traffic. Many types of switches exist, including ATM switches, LAN switches, and various types of WAN switches.
Routers perform two basic activities: determining optimal routing paths and transporting information groups (typically called packets) through an internetwork. In the context of the routing process, the latter of these is referred to as switching. Although switching is relatively straightforward, path determination can be very complex
Friday, February 19, 2010
BORDER GATEWAY PROTOCOL
BGP Configuration for Cisco Routers October
I want to show a basic BGP configuration for Internet access. In our case, we have two carriers (Sprint & Level3) and we act as an enterprise company, which needs reliable Internet access.
As a precondition we need an Autonomous System Number (ASN) and an IP address block assigned to us. We have to apply ARIN / RIPE / APNIC / LACNIC / AFRINIC for this purpose. We assume that we have 6767 as our AS number and 193.93.93.0/24 as our official IP block.
To show some different conditions, our connected Level3 router is also the BGP router, but Sprint BGP router has been located 3 hops away.
! We are starting with router command with our ASN like EIGRP/OSPF configuration
router bgp 6767
! We have one router in our case and we don’t need IGP / BGP synchronization it is default in newest IOSes
no synchronization
! To have some idea about our peering history we are recording events
bgp log-neighbor-changes
! We are announcing our network
network 193.93.93.0
! Our first neighbor is Sprint, we have to define neighbor ASN
neighbor 122.22.33.1 remote-as 1239
! Descriptions are always helpful
neighbor 122.22.33.1 description Sprint
! Our bgp neighbor in Sprint 3 hops away
neighbor 122.22.33.1 ebgp-multihop 3
! Sprint will use our Loopback IP (193.93.94.1) for us as the neighbor
neighbor 122.22.33.1 update-source Loopback 0
! If we have enough memory, we can prevent BGP session resets on inbound updates
neighbor 122.22.33.1 soft-reconfiguration inbound
! We won’t announce any network other than ourselves
neighbor 122.22.33.1 filter-list 1 out
! Now the Level 3
neighbor 111.11.11.1 remote-as 3356
neighbor 111.11.11.1 description LevelThree
neighbor 111.11.11.1 soft-reconfiguration inbound
neighbor 111.11.11.1 filter-list 1 out
no auto-summary
!
! Sprint BGP bridgehead is not directly connected to our router
! We must add necessary routing
ip route 122.22.33.1 255.255.255.255 122.22.22.1
!
! This filter means we are not announcing Sprint networks to Level3 or vice versa.
ip as-path access-list 1 permit ^$
Network Topology
network topology: The specific physical, i.e., real, or logical, i.e., virtual, arrangement of the elements of a network. Note 1: Two networks have the same topology if the connection configuration is the same, although the networks may differ in physical interconnections, distances between nodes, transmission rates, and/or signal types. Note 2: The common types of network topology are illustrated [refer to the figure on this page] and defined in alphabetical order below:
bus topology: A network topology in which all nodes, i.e., stations, are connected together by a single bus.
fully connected topology: A network topology in which there is a direct path (branch) between any two nodes. Note: In a fully connected network with n nodes, there are n(n-1)/2 direct paths, i.e., branches. Synonym fully connected mesh network.
hybrid topology: A combination of any two or more network topologies. Note 1: Instances can occur where two basic network topologies, when connected together, can still retain the basic network character, and therefore not be a hybrid network. For example, a tree network connected to a tree network is still a tree network. Therefore, a hybrid network accrues only when two basic networks are connected and the resulting network topology fails to meet one of the basic topology definitions. For example, two star networks connected together exhibit hybrid network topologies. Note 2: A hybrid topology always accrues when two different basic network topologies are connected.
linear topology: See bus topology.
mesh topology: A network topology in which there are at least two nodes with two or more paths between them.
ring topology: A network topology in which every node has exactly two branches connected to it.
star topology: A network topology in which peripheral nodes are connected to a central node, which rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, including the originating node. Note 1: All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. Note 2: The failure of a transmission line, i.e., channel, linking any peripheral node to the central node will result in the isolation of that peripheral node from all others. Note 3: If the star central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time, i.e., to and from the central node, plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems. (188)
tree topology: A network topology that, from a purely topologic viewpoint, resembles an interconnection of star networks in that individual peripheral nodes are required to transmit to and receive from one other node only, toward a central node, and are not required to act as repeaters or regenerators. (188) Note 1: The function of the central node may be distributed. Note 2: As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. Note 3: A single-point failure of a transmission path within a distributed node will result in partitioning two or more stations from the rest of the network.
bus topology: A network topology in which all nodes, i.e., stations, are connected together by a single bus.
fully connected topology: A network topology in which there is a direct path (branch) between any two nodes. Note: In a fully connected network with n nodes, there are n(n-1)/2 direct paths, i.e., branches. Synonym fully connected mesh network.
hybrid topology: A combination of any two or more network topologies. Note 1: Instances can occur where two basic network topologies, when connected together, can still retain the basic network character, and therefore not be a hybrid network. For example, a tree network connected to a tree network is still a tree network. Therefore, a hybrid network accrues only when two basic networks are connected and the resulting network topology fails to meet one of the basic topology definitions. For example, two star networks connected together exhibit hybrid network topologies. Note 2: A hybrid topology always accrues when two different basic network topologies are connected.
linear topology: See bus topology.
mesh topology: A network topology in which there are at least two nodes with two or more paths between them.
ring topology: A network topology in which every node has exactly two branches connected to it.
star topology: A network topology in which peripheral nodes are connected to a central node, which rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, including the originating node. Note 1: All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only. Note 2: The failure of a transmission line, i.e., channel, linking any peripheral node to the central node will result in the isolation of that peripheral node from all others. Note 3: If the star central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time, i.e., to and from the central node, plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems. (188)
tree topology: A network topology that, from a purely topologic viewpoint, resembles an interconnection of star networks in that individual peripheral nodes are required to transmit to and receive from one other node only, toward a central node, and are not required to act as repeaters or regenerators. (188) Note 1: The function of the central node may be distributed. Note 2: As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. Note 3: A single-point failure of a transmission path within a distributed node will result in partitioning two or more stations from the rest of the network.
Network Basic Terms
Examples of network operating systems
The following list includes some of the more popular peer-to-peer and client/server network operating systems.
• AppleShare
• Microsoft Windows Server
• Novell Netware
10Base2 - Ethernet specification for thin coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 185 meters per segment.
10Base5 - Ethernet specification for thick coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 500 meters per segment.
10BaseF - Ethernet specification for fiber optic cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 2000 meters per segment.
10BaseT - Ethernet specification for unshielded twisted pair cable (category 3, 4, or 5), transmits signals at 10 Mbps (megabits per second) with a distance limit of 100 meters per segment.
100BaseT - Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 100 Mbps (megabits per second) with a distance limit of 100 meters per segment.
1000BaseTX -Ethernet specification for unshielded twisted pair cabling that is used to trasmit data at 1 Gbps (gigabits per second) with a distance limitation of 220 meters per segment.
Asynchronous Transfer Mode (ATM) - A network protocol that transmits data at a speed of 155 Mbps and higher. It is most often used to interconnect two or more local area networks.
AppleTalk - Apple Computer's network protocol originally designed to run over LocalTalk networks, but can also run on Ethernet and Token Ring.
AUI Connector (Attachment Unit Interface) - A 15 pin connector found on Ethernet cards that can be used for attaching coaxial, fiber optic, or twisted pair cable.
Backbone - A cable to which multiple nodes or workstations are attached.
Bit - Binary digit in the binary numbering system. Its value can be 0 or 1. In an 8-bit character scheme, it takes 8 bits to make a byte (character) of data.
BNC Connector (Bayone-Neill-Concelman) - Standard connector used to connect 10Base2 coaxial cable.
Bridge - Devices that connect and pass packets between two network segments that use the same communications protocol.
Cable - Transmission medium of copper wire or optical fiber wrapped in a protective cover.
Client/Server - A networking system in which one or more file servers (Server) provide services; such as network management, application and centralized data storage for workstations (Clients).
CSMA/CA - Carrier Sense Multiple Access Collision Avoidance is a network access method in which each device signals its intent to transmit before it actually does so. This prevents other devices from sending information, thus preventing collisions from occurring between signals from two or more devices. This is the access method used by LocalTalk.
CSMA/CD - Carrier Sense Multiple Access Collision Detection is a network access method in which devices that are ready to transmit data first check the channel for a carrier. If no carrier is sensed, a device can transmit. If two devices transmit at once, a collision occurs and each computer backs off and waits a random amount of time before attempting to retransmit. This is the access method used by Ethernet.
Coaxial Cable - Cable consisting of a single copper conductor in the center surrounded by a plastic layer for insulation and a braided metal outer shield.
Concentrator - A device that provides a central connection point for cables from workstations, servers, and peripherals. Most concentrators contain the ability to amplify the electrical signal they receive.
DIN - A plug and socket connector consisting of a circular pattern of pins in a metal sleeve. This type of connector is commonly seen on keyboards.
Dumb Terminal - Refers to devices that are designed to communicate exclusively with a host (main frame) computer. It receives all screen layouts from the host computer and sends all keyboard entry to the host. It cannot function without the host computer.
E-mail - An electronic mail message sent from a host computer to a remote computer.
End User - Refers to the human executing applications on the workstation.
Ethernet - A network protocol invented by Xerox Corporation and developed jointly by Xerox, Intel and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps (megabits per second).
Expansion Slot - Area in a computer that accepts additional input/output boards to increase the capability of the computer.
Fast Ethernet - A new Ethernet standard that supports 100 Mbps using category 5 twisted pair or fiber optic cable.
Fiber Distributed Data Interface (FDDI) - A network protocol that is used primarily to interconnect two or more local area networks, often over large distances.
Fiber Optic Cable - A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity. It has the ability to carry more information over much longer distances.
File Server - A computer connected to the network that contains primary files/applications and shares them as requested with the other computers on the network. If the file server is dedicated for that purpose only, it is connected to a client/server network. An example of a client/server network is Novell Netware. All the computers connected to a peer-to-peer network are capable of being the file server. Two examples of peer-to-peer networks are LANtastic and Windows for Workgroups.
Gigabit Ethernet - An Ethernet protocol that raises the transmission rates to 1 Gbps (gigabits per second). It is primarily used for a high speed backbone of a network.
Gigabyte (GB) - One billion bytes of information. One thousand megabytes.
Hub - A hardware device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat but merely split signals sent through them).
Infrared - Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum.
Intranet - Network internal to an organization that uses Internet protocols.
Internet - A global network of networks used to exchange information using the TCP/IP protocol. It allows for electronic mail and the accessing ad retrieval of information from remote sources.
LAN (Local Area Network) - A network connecting computers in a relatively small area such as a building.
Linear Bus - A network topology in which each node attaches directly to a common cable.
LocalTalk - Apple Corporation proprietary protocol that uses CSMA/CA media access scheme and supports transmissions at speeds of 230 Kbps (Kilobits per second).
MAN (Metropolitan Area Network) - A network connecting computers over a large geographical area, such as a city or school district.
MAU (Multistation Access Unit) - A Token Ring wiring hub.
Modem (Modulator/Demodulator) - Devices that convert digital and analog signals. Modems allow computer data (digital) to be transmitted over voice-grade telephone lines (analog).
Multiplexer - A device that allows multiple logical signals to be transmitted simultaneously across a single physical channel.
Network Modem - A modem connected to a Local Area Network (LAN) that is accessible from any workstation on the network.
Network Interface Card (NIC) - A board that provides network communication capabilities to and from a computer.
Network Operating System (NOS) - Operating system designed to pass information and communicate between more than one computer. Examples include AppleShare, Novell NetWare, and Windows NT Server.
Node - End point of a network connection. Nodes include any device attached to a network such as file servers, printers, or workstations.
Node Devices - Any computer or peripheral that is connected to the network.
PCMCIA - An expansion slot found in many laptop computers.
Peer-to-Peer Network - A network in which resources and files are shared without a centralized management source.
Physical Topology - The physical layout of the network; how the cables are arranged; and how the computers are connected.
Point-to-Point - A direct link between two objects in a network.
Ports - A connection point for a cable.
Protocol -A formal description of a set of rules and conventions that govern how devices on a network exchange information.
RAID (Redundant Array of Inexpensive Disks) - A configuration of multiple disks designed to preserve data after a disk casualty.
RAM (Random Access Memory) - The working memory of a computer where data and programs are temporarily stored. RAM only holds information when the computer is on.
Repeater - A device used in a network to strengthen a signal as it is passed along the network cable.
RJ-45 - Standard connectors used for unshielded twisted-pair cable.
Router -A device that routes information between interconnected networks. It can select the best path to route a message, as well as translate information from one network to another. It is similar to a superintelligent bridge.
SCSI (Small Computer Serial Interface) - An interface controller that allows several peripherals to be connected to the same port on a computer.
Segment - Refers to a section of cable on a network. In Ethernet networks, two types of segments are defined. A populated or trunk segment is a network cable that has one or more nodes attached to it. A link segment is a cable that connects a computer to an interconnecting device, such as a repeater or concentrator, or connects a interconnecting device to another interconnecting device.
Sneaker-Net - Refers to a manual method of sharing files in which a file is copied from a computer to a floppy disk, transported to a second computer by a person physically walking (apparently wearing sneakers) to the second computer, and manually transferring the file from floppy disk to the second computer.
Speed of Data Transfer - The rate at which information travels through a network, usually measured in megabits per second.
Star Topology - LAN topology in which each node on a network is connected directly to a central network hub or concentrator.
Star-Wired Ring - Network topology that connects network devices (such as computers and printers) in a complete circle.
Tape Back-Up - Copying all the data and programs of a computer system on magnetic tape. On tape, data is stored sequentially. When retrieving data, the tape is searched from the beginning of tape until the data is found.
Terminator - A device that provides electrical resistance at the end of a transmission line. Its function is to absorb signals on the line, thereby keeping them from bouncing back and being received again by the network.
Thicknet - A thick coaxial cable that is used with a 10Base5 Ethernet LAN.
Thinnet - A thin coaxial cable that is used with a 10Base2 Ethernet LAN.
Token - A special packet that contains data and acts as a messenger or carrier between each computer and device on a ring topology. Each computer must wait for the messenger to stop at its node before it can send data over the network.
Token Ring - A network protocol developed by IBM in which computers access the network through token-passing. Usually uses a star-wired ring topology.
Topology - There are two types of topology: physical and logical. The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Logical topology is the method used to pass the information between workstations. Issues involving logical topologies are discussed on the Protocol chapter
Transceiver (Transmitter/Receiver) - A Device that receives and sends signals over a medium. In networks, it is generally used to allow for the connection between two different types of cable connectors, such as AUI and RJ-45.
Tree Topology - LAN topology similar to linear bus topology, except that tree networks can contain branches with multiple nodes.
Twisted Pair - Network cabling that consists of four pairs of wires that are manufactured with the wires twisted to certain specifications. Available in shielded and unshielded versions.
USB (Universal Serial Bus) Port - A hardware interface for low-speed peripherals such as the keyboard, mouse, joystick, scanner, printer, and telephony devices.
WAN (Wide Area Network) - A network connecting computers within very large areas, such as states, countries, and the world.
Workgroup - A collection of workstations and servers on a LAN that are designated to communicate and exchange data with one another.
Workstation - A computer connected to a network at which users interact with software stored on the network.
The following list includes some of the more popular peer-to-peer and client/server network operating systems.
• AppleShare
• Microsoft Windows Server
• Novell Netware
10Base2 - Ethernet specification for thin coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 185 meters per segment.
10Base5 - Ethernet specification for thick coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 500 meters per segment.
10BaseF - Ethernet specification for fiber optic cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 2000 meters per segment.
10BaseT - Ethernet specification for unshielded twisted pair cable (category 3, 4, or 5), transmits signals at 10 Mbps (megabits per second) with a distance limit of 100 meters per segment.
100BaseT - Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 100 Mbps (megabits per second) with a distance limit of 100 meters per segment.
1000BaseTX -Ethernet specification for unshielded twisted pair cabling that is used to trasmit data at 1 Gbps (gigabits per second) with a distance limitation of 220 meters per segment.
Asynchronous Transfer Mode (ATM) - A network protocol that transmits data at a speed of 155 Mbps and higher. It is most often used to interconnect two or more local area networks.
AppleTalk - Apple Computer's network protocol originally designed to run over LocalTalk networks, but can also run on Ethernet and Token Ring.
AUI Connector (Attachment Unit Interface) - A 15 pin connector found on Ethernet cards that can be used for attaching coaxial, fiber optic, or twisted pair cable.
Backbone - A cable to which multiple nodes or workstations are attached.
Bit - Binary digit in the binary numbering system. Its value can be 0 or 1. In an 8-bit character scheme, it takes 8 bits to make a byte (character) of data.
BNC Connector (Bayone-Neill-Concelman) - Standard connector used to connect 10Base2 coaxial cable.
Bridge - Devices that connect and pass packets between two network segments that use the same communications protocol.
Cable - Transmission medium of copper wire or optical fiber wrapped in a protective cover.
Client/Server - A networking system in which one or more file servers (Server) provide services; such as network management, application and centralized data storage for workstations (Clients).
CSMA/CA - Carrier Sense Multiple Access Collision Avoidance is a network access method in which each device signals its intent to transmit before it actually does so. This prevents other devices from sending information, thus preventing collisions from occurring between signals from two or more devices. This is the access method used by LocalTalk.
CSMA/CD - Carrier Sense Multiple Access Collision Detection is a network access method in which devices that are ready to transmit data first check the channel for a carrier. If no carrier is sensed, a device can transmit. If two devices transmit at once, a collision occurs and each computer backs off and waits a random amount of time before attempting to retransmit. This is the access method used by Ethernet.
Coaxial Cable - Cable consisting of a single copper conductor in the center surrounded by a plastic layer for insulation and a braided metal outer shield.
Concentrator - A device that provides a central connection point for cables from workstations, servers, and peripherals. Most concentrators contain the ability to amplify the electrical signal they receive.
DIN - A plug and socket connector consisting of a circular pattern of pins in a metal sleeve. This type of connector is commonly seen on keyboards.
Dumb Terminal - Refers to devices that are designed to communicate exclusively with a host (main frame) computer. It receives all screen layouts from the host computer and sends all keyboard entry to the host. It cannot function without the host computer.
E-mail - An electronic mail message sent from a host computer to a remote computer.
End User - Refers to the human executing applications on the workstation.
Ethernet - A network protocol invented by Xerox Corporation and developed jointly by Xerox, Intel and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps (megabits per second).
Expansion Slot - Area in a computer that accepts additional input/output boards to increase the capability of the computer.
Fast Ethernet - A new Ethernet standard that supports 100 Mbps using category 5 twisted pair or fiber optic cable.
Fiber Distributed Data Interface (FDDI) - A network protocol that is used primarily to interconnect two or more local area networks, often over large distances.
Fiber Optic Cable - A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity. It has the ability to carry more information over much longer distances.
File Server - A computer connected to the network that contains primary files/applications and shares them as requested with the other computers on the network. If the file server is dedicated for that purpose only, it is connected to a client/server network. An example of a client/server network is Novell Netware. All the computers connected to a peer-to-peer network are capable of being the file server. Two examples of peer-to-peer networks are LANtastic and Windows for Workgroups.
Gigabit Ethernet - An Ethernet protocol that raises the transmission rates to 1 Gbps (gigabits per second). It is primarily used for a high speed backbone of a network.
Gigabyte (GB) - One billion bytes of information. One thousand megabytes.
Hub - A hardware device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat but merely split signals sent through them).
Infrared - Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum.
Intranet - Network internal to an organization that uses Internet protocols.
Internet - A global network of networks used to exchange information using the TCP/IP protocol. It allows for electronic mail and the accessing ad retrieval of information from remote sources.
LAN (Local Area Network) - A network connecting computers in a relatively small area such as a building.
Linear Bus - A network topology in which each node attaches directly to a common cable.
LocalTalk - Apple Corporation proprietary protocol that uses CSMA/CA media access scheme and supports transmissions at speeds of 230 Kbps (Kilobits per second).
MAN (Metropolitan Area Network) - A network connecting computers over a large geographical area, such as a city or school district.
MAU (Multistation Access Unit) - A Token Ring wiring hub.
Modem (Modulator/Demodulator) - Devices that convert digital and analog signals. Modems allow computer data (digital) to be transmitted over voice-grade telephone lines (analog).
Multiplexer - A device that allows multiple logical signals to be transmitted simultaneously across a single physical channel.
Network Modem - A modem connected to a Local Area Network (LAN) that is accessible from any workstation on the network.
Network Interface Card (NIC) - A board that provides network communication capabilities to and from a computer.
Network Operating System (NOS) - Operating system designed to pass information and communicate between more than one computer. Examples include AppleShare, Novell NetWare, and Windows NT Server.
Node - End point of a network connection. Nodes include any device attached to a network such as file servers, printers, or workstations.
Node Devices - Any computer or peripheral that is connected to the network.
PCMCIA - An expansion slot found in many laptop computers.
Peer-to-Peer Network - A network in which resources and files are shared without a centralized management source.
Physical Topology - The physical layout of the network; how the cables are arranged; and how the computers are connected.
Point-to-Point - A direct link between two objects in a network.
Ports - A connection point for a cable.
Protocol -A formal description of a set of rules and conventions that govern how devices on a network exchange information.
RAID (Redundant Array of Inexpensive Disks) - A configuration of multiple disks designed to preserve data after a disk casualty.
RAM (Random Access Memory) - The working memory of a computer where data and programs are temporarily stored. RAM only holds information when the computer is on.
Repeater - A device used in a network to strengthen a signal as it is passed along the network cable.
RJ-45 - Standard connectors used for unshielded twisted-pair cable.
Router -A device that routes information between interconnected networks. It can select the best path to route a message, as well as translate information from one network to another. It is similar to a superintelligent bridge.
SCSI (Small Computer Serial Interface) - An interface controller that allows several peripherals to be connected to the same port on a computer.
Segment - Refers to a section of cable on a network. In Ethernet networks, two types of segments are defined. A populated or trunk segment is a network cable that has one or more nodes attached to it. A link segment is a cable that connects a computer to an interconnecting device, such as a repeater or concentrator, or connects a interconnecting device to another interconnecting device.
Sneaker-Net - Refers to a manual method of sharing files in which a file is copied from a computer to a floppy disk, transported to a second computer by a person physically walking (apparently wearing sneakers) to the second computer, and manually transferring the file from floppy disk to the second computer.
Speed of Data Transfer - The rate at which information travels through a network, usually measured in megabits per second.
Star Topology - LAN topology in which each node on a network is connected directly to a central network hub or concentrator.
Star-Wired Ring - Network topology that connects network devices (such as computers and printers) in a complete circle.
Tape Back-Up - Copying all the data and programs of a computer system on magnetic tape. On tape, data is stored sequentially. When retrieving data, the tape is searched from the beginning of tape until the data is found.
Terminator - A device that provides electrical resistance at the end of a transmission line. Its function is to absorb signals on the line, thereby keeping them from bouncing back and being received again by the network.
Thicknet - A thick coaxial cable that is used with a 10Base5 Ethernet LAN.
Thinnet - A thin coaxial cable that is used with a 10Base2 Ethernet LAN.
Token - A special packet that contains data and acts as a messenger or carrier between each computer and device on a ring topology. Each computer must wait for the messenger to stop at its node before it can send data over the network.
Token Ring - A network protocol developed by IBM in which computers access the network through token-passing. Usually uses a star-wired ring topology.
Topology - There are two types of topology: physical and logical. The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Logical topology is the method used to pass the information between workstations. Issues involving logical topologies are discussed on the Protocol chapter
Transceiver (Transmitter/Receiver) - A Device that receives and sends signals over a medium. In networks, it is generally used to allow for the connection between two different types of cable connectors, such as AUI and RJ-45.
Tree Topology - LAN topology similar to linear bus topology, except that tree networks can contain branches with multiple nodes.
Twisted Pair - Network cabling that consists of four pairs of wires that are manufactured with the wires twisted to certain specifications. Available in shielded and unshielded versions.
USB (Universal Serial Bus) Port - A hardware interface for low-speed peripherals such as the keyboard, mouse, joystick, scanner, printer, and telephony devices.
WAN (Wide Area Network) - A network connecting computers within very large areas, such as states, countries, and the world.
Workgroup - A collection of workstations and servers on a LAN that are designated to communicate and exchange data with one another.
Workstation - A computer connected to a network at which users interact with software stored on the network.
Subscribe to:
Posts (Atom)