From: Jim McBurnett (jim@tgasolutions.com)
Date: Sat Dec 29 2007 - 10:32:18 ART
So in the end, either should be acceptable unless the task says something like
this:
1. Filter the (incoming,outgoing ) routes with the least processor
intensive method.
2. Filter the (incoming,outgoing ) routes in a manner that does not use
a prefix list.
3. Filter the (incoming,outgoing ) routes in a manner that does not use
an access list.
Thoughts?
jim
From: nhatphuc [mailto:nhatphuc@gmail.com]
Sent: Saturday, December 29, 2007 3:38 AM
To: Joseph Brunner
Cc: Jim McBurnett; ccielab@groupstudy.com
Subject: Re: BGP suppress maps
Ah, yes. So you have to understand what ACL and prefix-list can match:
A prefix-list cannot be used to match on arbitrary bit patterns like an
accesslist can. Prefix-lists cannot be used to check if a number is even or
odd, nor check if a number is divisible by 15, etc... Bit checking in a
prefix-list is sequential, and must start with the most significant (leftmost)
bit. (from IEWB)
Phuc
On Dec 29, 2007 3:26 PM, Joseph Brunner
<joe@affirmedsystems.com<mailto:joe@affirmedsystems.com>> wrote:
Actually that's not true. Prefix-lists can't filter odd/even networks
ACL's can, while matching prefix length.
Prefix-lists are rumored to be friendlier on the CPU though...
;)
-----Original Message-----
From: nobody@groupstudy.com<mailto:nobody@groupstudy.com>
[mailto:nobody@groupstudy.com<mailto:nobody@groupstudy.com>] On Behalf Of
nhatphuc
Sent: Saturday, December 29, 2007 3:02 AM
To: Jim McBurnett
Cc: ccielab@groupstudy.com<mailto:ccielab@groupstudy.com>
Subject: Re: BGP suppress maps
I think there's no difference in using Prefix-list and access-list for BGP
filtering. As long as you can match the route, both will be OK.
For me, I prefer prefix-list over access-list because it is built to match
prefixes.
Phuc
On Dec 28, 2007 9:15 AM, Jim McBurnett <
jim@tgasolutions.com<mailto:jim@tgasolutions.com>> wrote:
> Ok,
> I am working on BGP suppress maps and keep going back to the difference
> between prefix lists and standard ACLS on the route map.
> Both work.
>
> I would assume that if the task does not specifically state that you use
> prefix lists or does not say do not use an access-list, that it is fine.
>
> But am I missing some larger picture due to my foggy brain?
>
> Thanks,
> Jim
>
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