Defining Communities

You can create a named community and include it in a routing policy with the community match condition (described in Table 12).

You can configure community and extended communities attributes to be included in BGP update messages. The community attribute is only four octets. The BGP extended communities attribute provides a larger range (eight octets) for grouping or categorizing communities. You can use community and extended communities attributes to trigger routing decisions, such as acceptance, rejection, preference, or redistribution.

The community-ids format varies according to the type of attribute that you use. The BGP community attribute format is as-number:community-value. The BGP extended communities attribute format is type:administrator:assigned-number.

When specifying community-ids for the community attribute, you can use UNIX-style regular expressions. Regular expressions are not supported for the extended communities attributes.

To define communities, you perform the following tasks:

• Configuring the Community Attribute
• Configuring the Extended Communities Attribute
• Inverting Community Matches
• Configuring Link Bandwidth