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BPG route filtering

Hello all,

Question. I have worked at many compaines and I always see route filtering performed the same way when using BGPv4. Prefix list. Why do admins use this method. Dont route-maps/distribute list perform the same function ?

Look forward to the great answers !

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BPG route filtering


Hi Michael,

we use prefix lists because it is capable of storing ip address information in a efficient structure (Permit/Deny), capable of defining one ip address or a range of prefixes. it is sequenced so we can insert different entries in one list and then simply bind it to a bgp neighbor.

you can also use access-lists for bgp route filtering but its not as effective as prefix lists.

route-maps themselvs use an ACL or a Prefix list for their match clause, you never want to wrap a thing into another thing and give it to your router, do u? distribute list is for IGP use.

are you THE Michael Moore? jk

plz Rate if it helped.


Soroush.

Hope it Helps!

Soroush.
New Member

BPG route filtering

lol !  I am that Michael Moore. I decided film making was much to hard work for me

Thank you on answering my question. Distribute list is only for IGPs and cannot be incorporated into EGP ?

So the only reason why we choose prefix-list really is based on organization. Everything else route-maps can do but the function is albeit differnt (match criteria and modify (set) packets).

In the case of BGP I often see it this way. Prefix-list created. Route-map created that references the prefix-list. Finally in the BGP neighbor statement we are filtering traffic based on that route map which is based on the prefix list. Does that make sense ? If so then are we not wrapping a thing into another thing ?

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