Bgp Configuration; Bgp Overview - Zte ZXR10 5900E Series User Manual

5
C h a p t e r

BGP Configuration

Table of Contents

BGP Overview ...................................................................45

Configuring BGP ................................................................46
BGP Configuration Example.................................................61
BGP Maintenance and Diagnosis ..........................................63
BGP Overview
Border Gateway Protocol (BGP) is an inter-area routing protocol.
BGP exchanges Network Layer Reachable Information (NLRI) be-
tween ASs that run BGP. This information includes a list of the ASs
that the routes pass. They are enough for creating a diagram indi-
cating the AS connection state. This makes the AS-based routing
policy possible and solves the route loop problem.
BGP Version 4 (BGP4), defined in RFC1771, supports CIDR, super-
net, subnet, route aggregation, and route filtering, and is widely
used on the Internet currently.
Border Gateway Protocol (BGP) is an interautonomous system
routing protocol. An autonomous system is a network or group
of networks under a common administration and with common
routing policies.
BGP is used to exchange routing information for the Internet and is
the protocol used between Internet service providers (ISP). Cus-
tomer networks, such as universities and corporations, usually
employ an Interior Gateway Protocol (IGP) such as RIP or OSPF for
the exchange of routing information within their networks. Cus-
tomers connect to ISPs, and ISPs use BGP to exchange customer
and ISP routes. When BGP is used between autonomous systems
(AS), the protocol is referred to as External BGP (EBGP). If a ser-
vice provider is using BGP to exchange routes within an AS, then
the protocol is referred to as Interior BGP (IBGP).
AS indicator is a 16-bit value ranging from 1 to 65535 of which
the numbers from 1 to 32767 are available for allocation. Those
from 32768 to 64511 are reserved. Those from 64512 to 65534
are used for private ASs (similar to private network addresses in
IP addresses).
BGP runs on the basis of a reliable transfer protocol with TCP as its
underlying protocol and TCP port 179. Routers running BGP first
set up a TCP connection and then exchange all the routing table
information after authentication. After that when the routing table
Confidential and Proprietary Information of ZTE CORPORATION 45