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Community Member

ip prefix-list on sub-interface

Hi

Is it possible to use a ip prefix-list on a sub-interface?

Alan

7 REPLIES
Hall of Fame Super Gold

Re: ip prefix-list on sub-interface

ip prefix-list to do what ?

Re: ip prefix-list on sub-interface

Hi Alan,

Prefix-lists are mainly used for route filtering with dynamic routing protocols or with attribute(s) manipulation with BGP, it is not used for packet filtering like ACLs, and thus can't be applied under interfaces.

BR,

Mohammed Mahmoud.

Re: ip prefix-list on sub-interface

Hi Alan,

I completely agree with Mohammed. Prefix-list has been designed for control plane(Drawing network map) so It cannot be used for filtering routes as ACL does at interface-level.

HTH

Thot

Community Member

Re: ip prefix-list on sub-interface

Hi

I agree with you that it is used to filter route. I have an example:

If I had 3 router connected via frame relay in a hub and spoke design and R1 is the hub. R1 is connected with a sub-interface. If i want to advertise only a default route out R1 serial interface. I use a default originate and a prefix that permit only 0.0.0.0/0 .

Problem is that I still get other route advertised out R1 serial sub-interface. If dun configure a sub-interface . it work.

May i know why is this so. Hope u know wat i am writing. hehe

Thanks in advance

Re: ip prefix-list on sub-interface

Hi,

Can you please post your configuration.

BR,

Mohammed Mahmoud.

Re: ip prefix-list on sub-interface

Which routing protocol are you using?

Hall of Fame Super Gold

Re: ip prefix-list on sub-interface

I wonder if there might be some confusion about how the prefix list is used relative to subinterfaces. Most of the comments about it not working focus on the possibility that it would be configured in subinterface config mode directly on the subinteface. But there is another possibility which is that the prefix list may be configured under the routing protocol as part of a distribute list and associated with the subinterface - which would work. Perhaps this could be looked at as prefix list working on the subinterface.

Perhaps the original poster can clarify which usage he is talking about?

HTH

Rick

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