Bgp; Bgp Introduction - Edge-Core ES4624-SFP Routing Management Manual

Remote address 3ffe:5678:3::1/128
Transmit Delay is 1 sec, State Point-To-Point,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Adjacency state Up

1.8 BGP

1.8.1 BGP Introduction

BGP stands for a Border Gateway Protocol.It's a dynamic routing protocol inter-autonomous
system. Its basic function is automatically exchanging routing information without loops. By
exchanging routing reachable information with autonomous number of AS sequence attributes,
BGP could create autonomous topological map to eliminate routing loop and implement policies
configured by users. Generally, the switches in an AS may use several IGPs (Interior Gateway
Protocol) in order to exchange routing information in the AS, such as RIP and OSPF which are
IGPs; and exchange information among ASes with EGP (Exterior Gateway Protocol). For
example, BGP is one kind of EGP. The AS is usually established on a single administrative
department. BGP is often used on the switches among ISPs or the departments of Multi-national
Corporation.
BGP has been used since1989, its earliest three versions are RFC1105 （BGP-1） 、 RFC1163
（BGP-2）and RFC1267（BGP-3）.Currently, the most popular one is RFC1771（BGP-4）. The
ES4624-SFP/ES4626-SFP switch supports BGP-4.
Characteristics of BGP-4
1．
BGP-4 is suitable for the distributed structure and supports Classless InterDomain Routing
(CIDR). BGP-4 is becoming the virtual exterior routing protocol standard used for the global
Internet. The features of BGP-4 are as follows.
BGP is an exterior routing protocol, unlike interior routing protocol, such as OSPF and RIP,
BGP can't discovery and calculate routes, but it can control the transmission of routes and select
the best route.
By carrying AS routing information in the updating route, the problem of Routing Loops can
be resolved
BGP uses TCP on port 179 as its transport protocol, this could enhance the reliability of the
protocol.
BGP-4 supports CIDR (Classless InterDomain Routing), which is an important improvement
to BGP-3. CIDR has a brand new way to look on IP address; it doesn't distinguish class A , Class
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