Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 385)

Feature ICX 6430 ICX 6450 FCX ICX 6610 ICX 6650 FSX 800
FSX 1600 ICX 7750
BGP4 AS4 Confederation Error
Checking No 08.0.01 14 08.0.01 08.0.01 08.0.01 08.0.01 08.0.10
RTM Scalability Enhancement No 08.0.01 14 08.0.01 08.0.01 08.0.01 08.0.01 08.0.10
Static BGP4 Networks No 08.0.01 14 08.0.01 08.0.01 08.0.01 08.0.01 08.0.10
BGP4 overview
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 AS 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.
Devices within an AS can use different Interior Gateway Protocols (IGPs) such as RIP and OSPF to
communicate with one another. However, for devices in different autonomous systems to communicate,
they need to use an EGP. BGP4 is the standard EGP used by Internet devices and therefore is the
EGP implemented on Brocade devices.
This is a simple example of two BGP4 ASs. Each AS contains three BGP4 devices. All of the BGP4
devices within an AS communicate using IBGP. BGP4 devices communicate with other autonomous
systems using EBGP. Notice that each of the devices also is running an Interior Gateway Protocol
(IGP). The devices in AS1 are running OSPF and the devices in AS2 are running RIP. The device can
be configured to redistribute routes among BGP4, RIP, and OSPF. They also can redistribute static
routes.
FIGURE 28 Example BGP4 autonomous systems
Relationship between the BGP4 route table and the IP route table
The device BGP4 route table can have multiple routes or paths to the same destination, which are
learned from different BGP4 neighbors. A BGP4 neighbor is another device that also is running BGP4.
BGP4 neighbors communicate using Transmission Control Protocol (TCP) port 179 for BGP4
BGP4 overview
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