RE: Prefix filtering (BGP)

From: Zaitsev DN (Dmitry) (DNZaitsev@xxxxxxxxxx)
Date: Fri May 26 2000 - 20:20:28 GMT-3


   
I think you can achieve the same result by using these two:

ip route 160.0.0.0 255.0.0.0 null 0
aggregate-address 160.0.0.0 255.0.0.0 summary-only

-----Original Message-----
From: Earl Aboytes [mailto:earl@linkline.com]
Sent: Friday, May 26, 2000 5:10 PM
To: ccielab@groupstudy.com
Subject: Prefix filtering (BGP)

Here is a kewl question.

Can anyone explain what is going on here?
Using access lists to filter supernets is a bit tricky. Assume, for
example, that a router has different subnets of 160.10.x.x and you want to
advertise 160.0.0.0/8 only. The following access list would permit
160.0.0.0/8, 160.0.0.0/9 and so on (remember, this is a class B address
space). access-list 1 permit 160.0.0.0 0.0.0.255

To restrict the update to 160.0.0.0/8 only, you have to use an extended
access list, such as the following:
  access-list 101 permit ip 160.0.0.0 0.255.255.255 255.0.0.0 0.255.255.255

What are they talking about!?!?!?!?
To me it looks like the destination network is 255.0.0.0/8. Is that what is
supposed to be going on here? Can anyone shed some light on this?



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