Overview Of Bgp4; The Ip Route Table - Dell PowerConnect B-FCXs Configuration Manual

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Overview of BGP4

BGP4 is the standard Exterior Gateway Protocol (EGP) used on the Internet to route traffic between

Autonomous Systems (AS) and to maintain loop-free routing. An autonomous system is a collection

of networks that share the same routing and administration characteristics. For example, a

corporate intranet consisting of several networks under common administrative control might be

considered an AS. The networks in an AS can but do not need to run the same routing protocol to

be in the same AS, nor do they need to be geographically close.

Routers within an AS can use different Interior Gateway Protocols (IGPs) such as RIP and OSPF to

communicate with one another. However, for routers in different autonomous systems to

communicate, they need to use an EGP. BGP4 is the standard EGP used by Internet routers and

therefore is the EGP implemented on Layer 3 Switches.

contains three BGP4 switches. All of the BGP4 switches within an AS communicate using IBGP.

BGP4 switches communicate with other autonomous systems using EBGP. Notice that each of the

switches also is running an Interior Gateway Protocol (IGP). The switches in AS1 are running OSPF

and the switches in AS2 are running RIP. Layer 3 Switches can be configured to redistribute routes

among BGP4, RIP, and OSPF. They also can redistribute static routes.

Relationship between the BGP4 route table and

The Layer 3 Switch BGP4 route table can have multiple routes to the same destination, which are

learned from different BGP4 neighbors. A BGP4 neighbor is another switch that also is running

BGP4. BGP4 neighbors communicate using Transmission Control Protocol (TCP) port 179 for BGP

communication. When you configure the Layer 3 Switch for BGP4, one of the configuration tasks

you perform is to identify the Layer 3 Switch BGP4 neighbors.

on page 982 shows a simple example of two BGP4 autonomous systems. Each AS

Example BGP4 autonomous systems

PowerConnect B-Series FCX Configuration Guide

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