[c-nsp] BGP/OSPF Default Route Question

[Greg Schwimer]

This will work for you.  It assumes you receive a default route from 
your provider.  If the link goes down, you may still receive the default 
via IBGP, so you need to make the default-originate conditional:

router ospf 100
  ...
 default-information originate metric-type 1 route-map OSPF-ADV-DEFAULT  
! makes the advertisement conditional
!
route-map OSPF-ADV-DEFAULT permit 1000
! now match the default route from your provider
 match ip address DEFAULT-ROUTE-FROM-PROVIDER
! and make sure it's a type external (i.e. learned via EBGP)
 match route-type external
!
! For good measure
!
route-map OSPF-ADV-DEFAULT deny 65535
!
ip access-list standard DEFAULT-ROUTE-FROM-PROVIDER
 permit 0.0.0.0

HTH
Greg


Claydon, Tom wrote:

>I have a question regarding BGP and OSPF that I was hoping I could get
>some help with. Here's my scenario:
>
>We have two Cisco 7206VXR's (names are "RT1" and "RT2") that we are
>using as border routers, each with a fractional OC3 connection to our
>upstream provider, which is sending us a default route only. Those
>routers are tied to Cisco 3550's, which are redistributing routes
>through OSPF, and all of our ISP gear is then tied to these switches.
>Everything works great.
>
>The big problem that we have is that if we have a circuit failure, the
>incoming & outgoing traffic does not switch over to the other router.
>After doing a lot of reading in Cisco's "BGP Design and Implementation",
>they suggest redistributing the default route from the upstream provider
>into OSPF - that way in case of a circuit failure, the default route
>drops out of the OSPF table, and the other router takes over.
>
>Does anyone have some examples of doing this? Are there other
>alternatives to doing what I've suggested above?
>
>Thanks,
> 
>= TC
> 
>--
>Tom Claydon, IT/ATM Network Engineer
>Dobson Telephone Company
>http://www.dobsonteleco.com
>
>
>
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