[c-nsp] BGP conditional advertisemet - NON-EXIST route map'saccess-list problem

[RPhookun at lecg.com]

I agree with Ivan in that the tracked prefix  in the Non-Exist-Map should 
be the ISP-1 infrastructure address because in its absence you wouldn't be 
receiving any other routes from ISP-1
However, the match of the tracked prefix is from the BGP table *not* the 
IP routing table and "match-as-path" can be very relevant in some 
topologies and its absence in the Non-Exist-Map can cause the conditional 
advertisement feature to break.

Cisco has an excellent example - "Configuring and Verifying the 
Conditional Advertisement Feature"

./Randy






"Ivan Pepelnjak" <ip at ioshints.info> 
Sent by: cisco-nsp-bounces at puck.nether.net
03/15/2009 12:48 PM

To
"'Burak Dikici'" <bdikici at gmail.com>
cc
cisco-nsp at puck.nether.net
Subject
Re: [c-nsp] BGP conditional advertisemet - NON-EXIST route 
map'saccess-list problem






That's the problem everyone has with the NON-EXIST-MAP :) Usually the IP
prefix used to address the ISP-1 infrastructure is the best bet.
 
The "match as-path" statement in the NON-EXIST-MAP is irrelevant (unless 
I'm
totally wrong about the match being made with the routes in the IP routing
table :).
 
Ivan


  _____ 

From: Burak Dikici [mailto:bdikici at gmail.com] 
Sent: Sunday, March 15, 2009 8:19 PM
To: Ivan Pepelnjak
Cc: Mateusz Blaszczyk; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] BGP conditional advertisemet - NON-EXIST route
map'saccess-list problem


Hi Ivan , 
 
 Ok than , what should i use for  NON-EXIST route-map's access-list ? 
Which
prefix should i trust from ISP-1 (Primary ISP) ? 
 Is it necessary to use  "match ip address" and "match as-path" statements
together in the  NON-EXIST route-map ?


On Sun, Mar 15, 2009 at 8:46 PM, Ivan Pepelnjak <ip at ioshints.info> wrote:


You can't use "permit any" because it would match any route in the IP
routing table (including the connected interfaces). The access list used 
in
NON-EXIST-MAP is used on the IP routing table, not on the BGP table 
(that's
why the AS path doesn't work either).

Ivan


> -----Original Message-----
> From: Burak Dikici [mailto:bdikici at gmail.com]
> Sent: Sunday, March 15, 2009 7:16 PM
> To: Mateusz Blaszczyk
> Cc: cisco-nsp at puck.nether.net

> Subject: Re: [c-nsp] BGP conditional advertisemet - NON-EXIST
> route map'saccess-list problem
>

> Hi Mateusz ,
>
> For better understanding , i have attached the topology
> screenshot and the router's configuration files. (By the way
> , this is a lab config.)
>
> In the attached Router's configuration ,
>
> access-list 65 permit 172.16.1.0 0.0.0.255
>
> command is used and with this command bgp conditional
> advertisement is working fine.
>
> But when i use ,
>
> access-list 65 permit any
>
> command , the conditional advertisement doesn't work.




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