Distributing default routes into BGP from two sites.

[Ashley Gibbon]

Hi

I have twenty sites. all are up and runnig on Verizons PIP network. One of the sites is our primary site providing WWW and core processing. Another site is a DR site which has WWW access incase of a disaster at primary site.

The networks routing protocol is BGP.

I want to distribute a default route and 10.22.0.0/16 into the network from two locations, one with a normal admin distance and another from the DR site with a high distance that will take over from the primary site in the event of a disaster.

What is the best way of acheiving this?

Ashley

[Giuseppe Larosa]

Hello Ashely,

if this a L3 VPN with SP you can use AS path prepending when advertising from DR site in the hope that each occurrence of the private BGP ASN will result in provider ASN in the AS path seen on the other VPN sites.

A better but more complex solution involves the use of BGP conditional advertising

see

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080094309.shtml

note:

Admin distance is local on a given router and cannot be propagated/adveritised so you need to play on BGP attributes.

Hope to help

Giuseppe

[Ashley Gibbon]

So this should work? I have found that if the non exist is the same as advertise are the same it will not work.

router bgp 201
no synchronization
bgp log-neighbor-changes
redistribute connected
neighbor 10.18.86.2 remote-as 65119
neighbor 10.18.186.2 remote-as 286
neighbor 10.18.186.2 advertise-map ADVERTISE non-exist-map NON-EXIST

no auto-summary

!
access-list 60 permit 0.0.0.0 0.0.0.0
access-list 65 permit 0.0.0.0 0.0.0.0
!
route-map NON-EXIST permit 10
match ip address 65
! 
route-map ADVERTISE permit 10
match ip address 60
!
!

[Giuseppe Larosa]

Hello Ashley,

you may need to check the non existance of some other IP prefixes for example a loopback address on the main site CE router

Hope to help

Giuseppe