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BGP prefix list

Posted on 2011-04-25
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Last Modified: 2012-05-11
Hello Experts,

Scenario: ISP has a an inbound prefix list for my AS:

ip prefix-list 2 seq 6 permit 50.50.0.0/21
ip prefix-list 2 seq 7 permit 50.50.8.0/21

and I currently have the same outbound.
If I modify miy outbound prefix list to them to:

ip prefix-list 2 seq 2 permit 50.50.0.0/20

Would this cause problems or will they automatically accept my announced network?


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Question by:trojan81
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rfc1180 earned 2000 total points
ID: 35464696
Depends on how they have their prefix list:

If they have a prefix list that matches

ip prefix-list x seq 2 permit 50.50.0.0/20

then yes, but you had already stated they have 2 prefix lists for the /21's:

ip prefix-list x seq 6 permit 50.50.0.0/21
ip prefix-list x seq 7 permit 50.50.8.0/21

then no; these are match exactly 21 bits, not the /20, however, if they have

ip prefix-list x seq 2 permit 50.50.0.0/20 le /21

then yes, you should be ok.

the 'ip prefix-list x seq 2 permit 50.50.0.0/20" is looking for an exact match of the /20.

Billy

 
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Author Closing Comment

by:trojan81
ID: 35464902
Exactly what I wanted to confirm which is that it has to match exactly due to the way they have it.
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