Cabletron Systems manual SmartSwitch Router User Reference Manual 153

Chapter 10: BGP Configuration Guide

The community attribute may be a single community or a set of communities. A maximum of 10 communities may be specified.

The community attribute can take any of the following forms:

•Specific community

The specific community consists of the combination of the AS-value and community ID.

•Well-known-community no-export

Well-known-community no-export is a special community which indicates that the routes associated with this attribute must not be advertised outside a BGP confederation boundary. Since the SSR’s implementation does not support Confederations, this boundary is an AS boundary.

For example, router SSR10 in Figure 12 has the following configuration:

ip-router policy create optional-attributes-list noexport well-known- community no-export

ip-router policy create bgp-export-destination 900to901dest autonomous- system 64901 optional-attributes-list noexport

ip-router policy export destination 900to901dest source 900to901src network all

ip-router policy export destination 900to901dest source 900to901dir network all

•Well-known-community no-advertise

Well-known-community no-advertise is a special community indicating that the routes associated with this attribute must not be advertised to other bgp peers. A packet can be modified to contain this attribute and passed to its neighbor. However, if a packet is received with this attribute, it cannot be transmitted to another BGP peer.

•Well-known-community no-export-subconfed

Well-known-community no-export-subconfed is a special community indicating the routes associated with this attribute must not be advertised to external BGP peers. (This includes peers in other members’ autonomous systems inside a BGP confederation.)

A packet can be modified to contain this attribute and passed to its neighbor. However, if a packet is received with this attribute, the routes (prefix-attribute pair) cannot be advertised to an external BGP peer.

•Well-known-community none

This is not actually a community, but rather a keyword that specifies that a received BGP update is only to be matched if no communities are present. It has no effect when originating communities.

SmartSwitch Router User Reference Manual 153