Zte ZXR10 5900E Series Configuration Manual page 125

Chapter 5
BGP Configuration
Table of Contents
BGP Overview............................................................................................................5-1
Configuring BGP ........................................................................................................5-4
Maintaining BGP ......................................................................................................5-55
BGP Configuration Examples ...................................................................................5-60
5.1 BGP Overview
Introduction to BGP
BGP is an inter-domain routing protocol used between ASs. By means of BGP, ASs can
exchange the information of network reachability between each other. The information
is a list of ASs where a route passes through, which is sufficient to set up a diagram to
indicate the connection status of the ASs. In this way, AS-based routing selection policy
is available, and BGP also solves the problem of route loop.
BGP of version 4 (BGP4) is the latest BGP version, which is defined in RFC1771. It has
the following features,
l
It supports to realize CIDR, supernet and subnet and so on.
l
It supports route aggregation.
l
BGP running is reliable. It uses Transfer Control Protocol (TCP) as its bottom layer
protocol. It uses TCP No.179 port.
l
It only sends route updating information.
l It sends keepalive packets regularly to make sure that TCP connection is well.
l It has consummate metric values.
l
It has abundant attributes and control functions.
l
It applies to large-scale network especially.
The session which is set up by BGP routers belonging to different ASs is called External
Border Gateway Protocol (EBGP) session, while a session which is set up between BGP
routers belonging to the same AS is called Internal Border Gateway Protocol (IBGP)
session.
An administrative area with independent routing policies is called an AS. The important
feature of an AS is that it has a unified internal route for another AS, and it has a consistent
topology for reachable destinations. The AS indicator is a value of 16-bit, ranging from 1
to 65535, where, 1–32767 are assignable, 32768–64511 are reserved, and 64512–65534
are used for private ASs (similar to private network addresses). When 16–bit AS number
SJ-20150114102049-003|2015-01-15 (R1.0)
5-1
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