Hi all,
I have two ISP router (router ISPA and router ISPB). These two router have a BGP session with my ISP and receives default route from them.

Both ISP router running also OSPF with my other internal router and generates a default route in ospf if the bgp default route received is available. I don't redistribute bgp into OSPF but I use "default-information originate" of ospf to generate the default route in ospf if bgp default route is available. The default route is seen as an E2 route by my other internal routers.



I also use route-map with the default-information originate command to do this before generating the default route in ospf:

- Router ISPA set the metric of its default route to 10 and tag it 1111.

- Router ISPB set it default route to 15 and tag it 2222.



My internal router choose so by default the router ISPA as it default route because of its smaller metric. What I want is to act on some other internal router so that it choose router ISPB as it default route.



So All internal router have two default route with metric 10 and 15, the metric of 10 is selected by default. But on the some other router,I would like to make manipulation to select the router ISPB as default route.

How can i do it ?

Thanks a lot.

As a CCIE candidate you should know that in the same area a metric can't be seen by one router as 15 and another router as 5. Only if this other router was in another area could you fool it.

And anyway, even if you could fool it what do you think would happen? This router that has been manipulated sends it traffic TOWARDS ISPB, it does not send it TO ISPB. The destination address does not change to ISPB. This is important. Why? Because let's say that the only way for the manipulated router to get to ISPB is through another router, when it gets to that other router, the other router will send it to ISPA. Again because the destination address is not ISPB, it's the end host.


You could run a tunnel, run BGP inside, or run MPLS and run BGP on this second box and then you can do it

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www.mellowd.co.uk/ccie/

Thanks mellowd,
In my case, some inside router can route directly to router ISPB or A and it's in this type of router i want to do the manipultaion.

Anyway, if i put in place two area (0 and 1). How to publish a default route with as best route ISPA in the area 0 and another default route or modification of the first default route in the area 1 as best route ISPB ?

Thanks.

First we need to see the topology. Give us a diagram

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www.mellowd.co.uk/ccie/

See attached a gn3 topology.
Router5 is ISPA and Router6 ISPB
I simulate a default route by configuration a static default route to router7.

Router1, 2, 5 and 6 is on area 1

Router 3, 4, 5 and 6 is on area0

What i need is generate a default route on area0 with area0 router choose router5 as best next-hop and generate default route on area1 with area1 router choose router6 as best next-hop.

Thanks.

I don't have gns3. export the topology as a picture and post that

_________________
www.mellowd.co.uk/ccie/

Another option (depending on your topology and which devices you wanted to route to where) would be to distribute the default route as a type-1 metric instead, that way if you were closer to the ISPA router you would go there, if you are closer to ISPB you would go there.

The same kind of behaviour could also be seen if you used the same metric for the E2 metrics, they would then use the forwarding metric as the tie breaker and go via the closer ASBR / ABR.

Once again though, this really depends on the topology, do a print screen from GNS and post it here along with which routers you are wanting to uses which ISP etc.

_________________
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David
CCIE R&S #38338, CCIP, CCNP

http://networkbroadcast.co.uk - My Blog
http://twitter.com/davidrothera

Hi,

See attached the topology.