Community Lists

A Community is an optional transitive BGP attribute. A community is a group of destinations that share some common attribute. It is used for route tagging. The BGP community attribute is a numerical value that can be assigned to a specific prefix and advertised to other neighbors. Communities can be used to mark a set of prefixes that share a common attribute. Upstream providers can use these markers to apply a common routing policy such as filtering or assigning a specific local preference or modifying other attributes. Use the Configure Community Lists page to create, copy and edit community list policy objects. You can create community list objects to use when you are configuring route maps or policy maps. You can use community lists to create groups of communities to use in a match clause of a route map. The community list is an ordered list of matching statements. Destinations are matched against the rules until a match is found.

You can use this object with FTD devices.

Procedure

Step 1

Select Objects > Object Management and choose Community List from the table of contents.

Step 2

Click Add Community List.

Step 3

In the Name field, specify a name for the community list object.

Step 4

Click Add on the New Community List Object window.

Step 5

Select the Standard radio button to indicate the community rule type.

Standard community lists are used to specify well-known communities and community numbers.

Note
You cannot have entries using Standard and entries using Expanded community rule types in the same Community List object.

  1. Select the Allow or Block options from the Action drop-down list to indicate redistribution access.

  2. In the Communities field, specify a community number. Valid values can be from 1 to 4294967295 or from 0:1 to 65534:65535.

  3. Select the appropriate Route Type.

    • Internet — Select to specify the Internet well-known community. Routes with this community are advertised to all peers (internal and external).
    • No Advertise — Select to specify the no-advertise well-known community. Routes with this community are not advertised to any peer (internal or external).
    • No Export — Select to specify the no-export well-known community. Routes with this community are advertised to only peers in the same autonomous system or to only other sub-autonomous systems within a confederation. These routes are not advertised to external peers.
Step 6

Select the Expanded radio button to indicate the community rule type.

Expanded community lists are used to filter communities using a regular expression. Regular expressions are used to specify patterns to match COMMUNITIES attributes.

  1. Select the Allow or Block options from the Action drop-down list to indicate redistribution access.

  2. Specify the regular expression in the Expressions field.

Step 7

Click Add.

Step 8

If you want to allow overrides for this object, check the Allow Overrides check box; see Allowing Object Overrides.

Step 9

Click Save.