Troubleshooting guide

Additional BGP Configuration

local-as Specifies routes that contain the reserved community number for

NO_EXPORT_SUBCONFED. Routes containing this attribute should not be advertised to external

BGP peers.

no-advertise Spe

cifies routes that contain the reserved community number for NO_ADVERTISE.

Routes containing this attribute should not be advertised to any BGP peer.

no-export

Specifies routes that contain the reserved community number for NO_EXPORT. Routes

containing this attribute should not be advertised to BGP peers outside a confederation boundary.

Table 1 below summarizes the well-known communities and the policy

expected for these

communities.

Table 1. Well-Known Communities

internet All peers

local-as Peers in the local AS

no-advertise No peers

no-export Internal peers only

After the community list has been defined, it must be referenced in a route map entry. Refer to Route

Map on page 23 for information on creating route maps. Refer to Filtering Routes According to

Community on page 27 for information on how to reference a community

list within the route map.

Defining a Community Policy

The community policy defines the action that will be taken on routes depending on the community

string attached to those routes. This can be used to set certain attributes, such as local preference or

metric, for routes in the community. The set commands are used to define the community policy on a

community string. These commands are issued within Route Map Configuration mode (refer to Route

Map on page 23) and the route map is applied outbound to a BGP neighbor (refer to Applying a Route

Map Entry to a BGP Neighbor on page 30

Use the set community command to select the peers to which a neighbor advertises routes in the

community:

(config-route-map)#set community <value> [add | internet | local-as | no-advertise | no-export]

Community Advertise To

Multiple communities can be specified by stringing several keywords in the same

command (for example, (config-comm-list)#permit local-as no-export).

Before placing a route in a community, you should contact your service provider and

discuss what options it supports for various communities. You should also consult your

organization’s policies.