Bgp Communities - Lenovo RackSwitch G8264CS Application Manual

BGP Communities

© Copyright Lenovo 2017
BGP communities are attribute tags that allow controlled distribution of routing
information based on an agreement between BGP peers. Communities are
commonly used by transit service providers to enable peering customers to choose
specific routing destinations for their outgoing routes. The transit service provider
would typically publish a list of well‐known or proprietary communities along
with their descriptions, and take it upon itself to advertise incoming routes
accordingly. For instance, an ISP may advertise that incoming routes tagged with
community XY:01 will be advertised only to European peers while incoming routes
tagged with community XY:02 will be advertised only to Asian peers.
The RackSwitch G8264CS can be configured to manage the community tags
applied to the outgoing route updates. It does not, however, modify any routing
decisions based on the community tags.
Up to 32 community tags can be applied to prefixes that pass a route‐map. Valid
values are between 0:0 and 65535:65535. Newly added communities will be
appended to any existing configured communities. To append communities to
prefixes that pass the route‐map, use the following commands:
RS 8264CS(config)# route-map <map number>
RS 8264CS(config-route-map)# set community {aa:nn [aa:nn]}
To remove all community tags from prefixes that pass the route‐map, use the
following command:
RS 8264CS(config-route-map)# set community none
To remove configured communities on a routemap, use the following command:
RS 8264CS(config-route-map)# no set community
Prefixes with communities are propagated unchanged if there is no routemap that
alters the community attribute and if the neighbor has community tags forwarding
enabled.
To enable or disable community tags forwarding for specific neighbors or neighbor
groups, use the following commands:
RS 8264CS(config)# router bgp
RS 8264CS(config-router-bgp)# neighbor 5 send-community
RS 8264CS(config-router-bgp)# no neighbor 6 send-community
RS 8264CS(config-router-bgp)# neighbor group 1 send-community
RS 8264CS(config-router-bgp)# no neighbor group 2 send-community
Chapter 28: Border Gateway Protocol
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