Type B Inter-AS :How to limit number of route-target ?

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Apr 8th, 2010
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Hi,


We came across one problem in our network that we get couple of prefix from our peering partner's customer with very long ( almost more than 100) RT on our ASBR. This caused huge problem with our legacy PE router and MP-BGP session with RR went down on all our PE.


What should be solution I should look on ASBR for Type-B NNI ? Is that something we can do to limit number of RT while doing peering with our peer ?


Regards,

Chintan

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Giuseppe Larosa Thu, 04/08/2010 - 08:44
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Hello Chintan,


the bgp rr-group can be used on a Route Reflector server to decide what  vpnv4 prefixes to reflect to clients referring to an ip extcommunity extended access-list using regular expression in address.family VPNv4 context

It is not a check on the number or RTs attached to the VPNv4 advertisement.



However, there is not , as far as I know, the equivalent of bgp max-as command that can decide the max acceptable AS path attribute length.


see

http://www.cisco.com/en/US/docs/ios/iproute_bgp/command/reference/irg_bgp1.html#wp1072398


Hope to help

Giuseppe

chintan-shah Thu, 04/08/2010 - 08:59
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Hi Giuseppe,


Yes, This could be one of solution which we are applying on ASBR itself but if correct RT comes with lot more number on prefix , create an issue.

I was thinking we do re-write of RT as per below :

http://www.ciscosystemsnetwork.org/en/US/docs/ios/12_2s/feature/guide/fsrtrw4.html#wp1027173


I guess this required per customer ( i.e. customer of our Type B peering partner) and we need to know RT and then one to one re-write completely , i mean delete whatever commign and add our own RT.


Does any one have expreince on this on live enviorment ?


Regards,

Chintan

Giuseppe Larosa Fri, 04/09/2010 - 01:42
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Hello Chintan,

I agree this route target rewrite feature could be the right tool for the job but as you noted a route-map clause is needed for each customer VPN and this clearly leads to a scalability problem


Hope to help

Giuseppe

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