Network Router User Manual

SmartSwitch Router User Reference Manual 151
Chapter 12: 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 13 has the following configuration:
• 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.
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