Overview Of Bgp4 - Foundry Networks FESX Manual

Foundry Configuration Guide for the FESX, FSX, and FWSX
Description
Removing route flap dampening
Clearing diagnostic buffers
BGP4 is described in RFC 1771. The Foundry implementation fully complies with RFC 1771. The Foundry BGP4
implementation also supports the following RFCs:
• RFC 1745 (OSPF Interactions)
• RFC 1997 (BGP Communities Attributes)
• RFC 2385 (TCP MD5 Signature Option)
• RFC 2439 (Route Flap Dampening)
• RFC 2796 (Route Reflection)
• RFC 2842 (Capability Advertisement)
• RFC 3065 (BGP4 Confederations)
To display BGP4 configuration information and statistics, see "Displaying BGP4 Information" on page 21-65.
This chapter shows the commands you need in order to configure the Foundry Layer 3 Switch for BGP4. For a
detailed list of all CLI commands, including syntax and possible values, see the Foundry Switch and Router
Command Line Interface Reference.
NOTE: Your Layer 3 Switch's management module must have 32MB or higher to run BGP4.

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 ASs to communicate, they need to use an EGP. BGP4 is the
standard EGP used by Internet routers and therefore is the EGP implemented on Foundry Layer 3 Switches.
Figure 21.1 on page 21-3 shows a simple example of two BGP4 ASs. Each AS contains three BGP4 routers. All
of the BGP4 routers within an AS communicate using IBGP. BGP4 routers communicate with other ASs using
EBGP. Notice that each of the routers also is running an Interior Gateway Protocol (IGP). The routers in AS1 are
running OSPF and the routers in AS2 are running RIP. Foundry Layer 3 Switches can be configured to redistribute
routes among BGP4, RIP, and OSPF. They also can redistribute static routes.
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Table 21.1: Chapter Contents
© Foundry Networks, Inc.
See Page
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December 2005