[c-nsp] BGP -> OSPF (Or another way?)

[Dale Shaw]

Hi,

On Wed, Jun 10, 2009 at 9:05 AM, <mb at adv.gcomm.com.au> wrote:
> I know redistributing bgp->ospf is considered a bad idea, but other than
> adding a static route, is there another option?

You could use a 'reliable static' (using IP SLA and the 'track'
keyword on the 'ip route' command) and redistribute that, but I'm not
sure it's any 'better' in this case, as long as you're only ever
redistributing a small number of routes. You could probably get
quicker convergence this way, depending on how connectivity to the
upstream fails.

http://www.cisco.com/en/US/docs/ios/12_3/12_3x/12_3xe/feature/guide/dbackupx.html

Assuming you pursue the BGP -> OSPF redistribution --

> Under ospf would it be
> redistribute bgp xxx route-map SUBNET_TO_INJECT_FROM_BGP

Don't forget the 'subnets' keyword.

> With the above route maps acl only allowing the /24 we are interested in?

Depending on your route-map config, yeah.

ip prefix-list BGP_TO_OSPF permit 192.168.55.0/24
!
route-map SUBNET_TO_INJECT_FROM_BGP
 match ip address prefix BGP_TO_OSPF
!
router ospf 1
 redistribute bgp 12345 subnets route-map SUBNET_TO_INJECT_FROM_BGP

This will inject anything matched in the 'BGP_TO_OSPF' prefix-list
into OSPF as a type-2 external ("O E2") route. This'll turn your BGP
router into an OSPF ASBR, if it's not already. Make sure it's not in a
stub area.

cheers,
Dale