Use this command to set the preference (also known as administrative distance) of BGP routes to specific destinations. You may enter up to 128 instances of this command. Two instances of this command may not have the same prefix and wildcard mask. If a distance command is configured that matches an existing distance command's prefix and wildcard mask, the new command replaces the existing command. There can be overlap between the prefix and mask configured for different commands. When there is overlap, the command whose prefix and wildcard mask are the longest match for a neighbor's address is applied to routes from that neighbor.
An ECMP route's distance is determined by applying distance commands to the neighbor that provided the best path.
The distance command is not applied to existing routes. To apply configuration changes to the distance command itself or the prefix list to which a distance command applies, you must force a hard reset of affected neighbors.
| Default | BGP assigns preference values according to the distance bgp command, unless overridden for specific neighbors or prefixes by this command. |
| Format | distance distance [prefix wildcard-mask [prefix-list]] |
| Mode | BGP Router Config |
| Parameter | Description |
|---|---|
| distance | The preference value for matching routes. The range is 1 to 255. |
| prefix wildcard-mask | [Optional] Routes learned from BGP peers whose address falls within this prefix are assigned the configured distance value. The wildcard-mask is an inverted network mask whose 1 bits indicate the don't care portion of the prefix. |
| prefix-list | [Optional] A prefix list can optionally be specified to limit the distance value to a specific set of destination prefixes learned from matching neighbors. |
Example: The following shows examples of the command.
Example 1: To set the preference value of the BGP route to 100.0.0.0/S from neighbor 10.1.1.1, use the following command:
(R1) (Config)# ip prefix-list pfx-list1 permit 100.0.0.0/8 (R1) (Config)# router bgp 1 (R1) (Config-router)# distance 25 10.1.1.1 0.0.0.0 pfx-list1
Example 2: To set the preference value to 12 for all BGP routes from neighbor 10.1.1.1, use the following distance command:
(R1) (Config-router)# distance 12 10.1.1.1 0.0.0.0
Example 3: To set the preference value of all routes within 100.0.0.0/S from any neighbor, use the following distance command:
(R1) (Config)# ip prefix-list pfx-list2 permit 100.0.0.0/8 ge 8 (R1) (Config)# router bgp 1 (R1) (Config-router)#distance 25 0.0.0.0 255.255.255.255 pfx-list2
