Chapter 16: Dynamic Routing Protocols
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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Border Gateway Protocol
Border Gateway Protocol (BGP) is the routing protocol used to exchange routing information across the Internet.
BGP was developed to allow interconnection between Internet Service Providers (ISPs), and to allow end-users to connect
to more than one ISP. BGP is a solution that can accommodate the vast expanse of the Internet, and also handle multiple
connections to unrelated routing domains.
BGP Version 4
BGP Version 4 (BGP-4) is the most widely deployed version of BGP.
BGP-4 provides the mechanisms for supporting Classless Inter-Domain Routing (CIDR). These mechanisms include:
Support for advertising a set of destinations as an IP prefix.
Eliminating the concept of network "class" within BGP.
BGP-4 also introduces mechanisms that allow aggregation of routes, including aggregation of Autonomous System (AS)
paths.
BGP-4 Implementation
The following points summarize BGP-4 implementation on the C4/c CMTS:
BGP-4 complies with RFC 1771 and the MIB RFC 1657.
If the C4/c CMTS is used in either an eBGP or iBGP configuration, it must be for an MSO’s internal network only. Given
the size of the C4/c CMTS hardware routing table, approximately 32K routes, the C4/c CMTS must not be defined as an
AS-border router running either eBGP or iBGP to the internet.
The C4/c CMTS supports a single instance of BGP, and it must be on the default VRF.
iBGP routes have a default administrative distance of 200.
eBGP routes have a default administrative distance of 20.
BGP-4 supports Autonomous System Confederations. This feature is useful in reducing full mesh configurations in iBGP.
A BGP AS is split into multiple sub-ASs. Within a sub-AS, there is a full mesh of iBGP.