bgp-community

Defines a BGP community string to be attached to selected route assertions.

bgp-community all <list>
 
bgp-community assert if-winner <list>
 
bgp-community assert if-in-winner-set <list>
 
bgp-community assert if-not-in-winner-set <list>
 
bgp-community match (invalid-winner | force-winner) community <A:B>
 

 
no bgp-community all
 
no bgp-community assert if-winner
 
no bgp-community assert if-in-winner-set
 
no bgp-community assert if-not-in-winner-set
 
no bgp-community match invalid-winner
 
no bgp-community match force-winner
 

• list--value of BGP community; can be one of the following:
• one or more community numbers, each in a:b format where a and b are integers in the range 1 through 65534 separated by a colon
• “”--two double quotes signifying an empty string; blocks inheritance of a BGP community value, resulting in no BGP community string
• one of the well-known values defined in RFC 1997, in the following forms:

• A:B--a community number, in a:b format where a and b are integers in the range 1 through 65534 separated by a colon

For all, must be in engine or policy configuration mode (config-engine or config-engine-policy).

For assert, must be in link mode at either the engine or policy level (config-engine-link or config-engine-policy-link).

For match, must be in link mode at the engine level (config-engine-link).

All modes require privileged-level access.

Use a command/keyword combination once per configuration mode (within each scope that will accept the command, there can be only one BGP community defined for a route).

None, except that, within a decision policy, if no values are explicitly set the globally set values (if any) will apply

The bgp-community command allows you to associate BGP community values with selected routes.

The values included in list will be applied to all routes that meet the criteria defined by the keyword used:

• all--values will be associated with all routes asserted by CNA (including BGP selected routes, if you have enabled assert-routes-matching-bgp), regardless of link
• assert if-winner--values will be associated with routes only when the specified link is the winner as determined by the CNA decision-maker process
• assert if-in-winner-set--values will be associated with routes only when the specified link is in the winner-set
• assert if-not-in-winner-set--values will be associate with routes when the specified link is not in the winner set
• match--when used with invalid-winner, will cause the link to be marked as invalid if the community matches a natural route

Setting a community value with the bgp-community all command will overwrite the default behavior, which is to associate the string no-export with all routes. If you want this behavior to remain in effect, you must explicitly include it in your list argument, at either the global level or within a decision policy.

If you override the no-export value at the global level, this behavior will be inherited by decision policies. If you want it added back for a specific policy, you must explicitly add it within that policy’s configuration.

You can use the bgp-community all command without arguments to remove the no-export value from route assertions.

If a condition has been set at both global and policy levels, the more specific condition will apply. For example, if you specify a community value with the keyword all at both levels, the string specified in the policy level will override the global string.

If you set list equal to a null string (“”), no BGP community value will be associated with the prefix at this configuration scope. The empty string blocks inheritance of the value from the previous level in the hierarchy.

Each BGP community list can have multiple components. Separate each value by a space character and enclose the entire list in double quotes:

bgp-community all “65001:1 65002:2 65003:3”
 

 

The bgp-community command should be used in place of the outbound-bgp-community (discontinued) command, which will not be supported in future CNA releases.

Use the no form of the command to remove the specified form of the command from the scope in which it is entered.

In the following configuration example, the BGP community value is set to 100:00 for the link named link_A if it is the winning link selected by CNA and to 1000:1000 if it is not in the winner set.:

module engine 1
 
   link link_A
 
     bgp-community assert if-winner 100:100
 
     bgp-community assert if-not-in-winner-set 1000:1000
 
   end
 

 

You can change these values for selected prefixes by creating a decision policy. For example, you can change the BGP community value to 1:1 when link_A is the winning link for a selected prefix and to nothing when it is not in the winner set for that prefix, by adding the following commands to your engine module configuration:

   decision-policy rule_A
 
     link link_A
 
       bgp-community assert if-winner 1:1
 
       bgp-community assert if-not-in-winner-set ""
 
     end
 
   end
 
   set-decision-policy 192.168.1.0/24
 
 end
 

 

In the example, the bgp-community assert if-not-in-winner-set command in the decision policy blocks inheritance of the if-not-in-winner-set value that was set at the config-engine level.