topic redist route from bgp to OSPF is sending more than the default route in General Topics

redist route from bgp to OSPF is sending more than the default route

dbrenipc — Wed, 26 May 2021 15:30:24 GMT

When we turned up BGP in the Palo with ExpressRoute, we started to receive 4 subnets from Microsoft.

The customer found that these subnets are being leaked into the Extreme Fabric through the OSPF adjacency to the Palo’s, where only Default route should be sent from the Palo to the Extreme. Not sure why this is happening, since it looks like there is a policy that should only send default route.

I have a case open, but am posting here due to long wait times.

Cheers-

Don

Re: redist route from bgp to OSPF is sending more than the default route

BPry — Thu, 27 May 2021 01:37:58 GMT

@dbrenipc,

There's really not enough information here to troubleshoot this without being able to look at your configuration. Seems like your redistribution profile is setup with an incorrect filter since it doesn't seem like you even want the 4 subnets redistributed to OSPF.

Re: redist route from bgp to OSPF is sending more than the default route

aleksandar.astardzhiev — Thu, 27 May 2021 10:14:23 GMT

Hi @dbrenipc ,

I believe this is caused by the redistribution profile you have configured. This is something that annoys me a lot - when you configure "Destination" in the redistribution profile, the prefix you put will not look for exact match, but it will match any prefix that falls under the configured prefix.

In your case I am almost certain that you have put 0.0.0.0/0 as destination for the redistribution profile. Which as you can guess will match all othe routes.

One way to fix this is to narrow down your redistrubtion profile filter -

- select the only the interface to which default is pointing

- select next-hop address to which default is pointing

That way no other route will match that redist profile. But this depends on your config

Another way would be to create additional redistribution profile:

- configure destination to match all prefixes that you don't want to redistribute to OSPF

- Set action to no-redist

- And set priority that is lower than what you have for the default route redist profile

Redistribution profiles are applied in order from lowest to highest priority, so this would work like firewall rule and redistribute only the prefix you have in the profile with action redistribute

Re: redist route from bgp to OSPF is sending more than the default route

dbrenipc — Thu, 27 May 2021 13:44:44 GMT

Further information:

redist profile has src: BGP detination 0.0.0.0/0 redist

in the export it says redistribute default route

I've found multiple docs that provide some conflicting info.

1 said NOT to use 0.0.0.0/0, and to only have the redistribute default route .

The other said to create a no-redist rule for the specific networks

then have the redist rule to probvide the default route wiht 0.0.0.0./0 specified.

I hope to lab it out asap.

thanks for your help - Don

Re: redist route from bgp to OSPF is sending more than the default route

dbrenipc — Thu, 27 May 2021 21:59:05 GMT

Thank you Alexander- I am going to lab this up when I have time..But I agree...

regards,

Don