IP Prefix-List

To create a Prefix-List you need tobe in global configuration mode :
ip prefix-list ( option ) ( name )
seq (sequence number ) ( permit or deny ) (x.x.x.x )/(x) then you can use le and ge or a combination of the 2 to modufy the way a prefix list rule matches a network prefex lenght.

le or ge can only be apply by using the following specific conditions :
/prefix-length < ge-value <= le-value

the network address prefix length must be less than the value that follows the ge keyword. Additionally, the value that follows the le keyword must be greater than or equal to the value that follows the ge keyword, if specified, or greater than the network address prefix length.

example :
le /32 will match any address within the subnet .

Don’t forget the deny explicit on each prefix-list
ip prefix-list “NAME” seq# permit 0.0.0.0/0 le 32

And at last we need to apply it on the routing protocol were using .
Example :

distribute-list prefix “NAME” gateway “NAME” IN or OUT
distribute-list prefix “NAME”¬†OUT or IN “Interface”

 

 

 

 

Leave a Comment