When Primary link restore back route still learn via CE_HQ instead MPLS

[r.hew]

Hi Sir,

Please refer my issue as below and attachment for log captured;

1) When primary link down at CE_Branch_1, it will triggered the ISDN to CE_HQ to communicate.

2) When the primary is up again at CE_Branch_1, the ISDN will be disconnected.

3) At CE_HQ, when show ip route the 10.106.15.0 network still appear in static route instead of OSPF route. Hence, LAN user at CE_Branch_1 will not able to access HQ anymore.

4) When sho ip route vrf COURTS at PEWBRF1, you can notice network 10.106.15.0 is still learned via 202.178.128.70 and not 178.28.0.20.

5) Have tried to manipulate the route-map with set local-preference = 50 and set weight = 0 for network 10.106.15.0 that being redistributed from OSPF into MPBGP at PEWBRF1 still doesn’t help. Furthermore, I encounter the route have become RIB-Failure when show ip bgp vpnv4 vrf COURTS.

6) At CE_HQ, there is floating static route being configured to point to CE_Branch_1’s LAN, ip route 10.106.15.0 255.255.255.0 128.1.1.15.

7) When show ip bgp vpnv4 vrf COURTS 10.106.15.0 and show ip route vrf COURTS 10.106.15.0 at PEWBRF1 the route 10.106.15.0 still prefer to come from CE_HQ. This is the problem, now the CE_HQ can not reach CE_Branch_1.

Please advise.

[maher]

Dear R.Hew,

Can I have a look at your router config on CE_Branch_1 and CE_HQ ? Do you have backdoor routing?

Are you using floating static routes?

regards,

maher

[r.hew]

Hi Maher,

I don't have the customer config but I believe their are running floating static routes at both the CE_Branch_1 & CE_HQ.

Thanks.

[maher]

Hi R.Hew,

Your implementation quite similar with my lab test, regarding the routes selection.Why the CE still prefer routes going to ISDN when the primary is up.

Perhaps need to find tune in the IGP ?

However, I did recover through sham-link:

http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1838/products_feature_guide09186a00800a8570.html

But from my experience, using normal leased line, not the isdn.

Just my 2 cens.

regards,

maher

[delroygordon]

I had a similar problem when using floating static routes with BGP for isdn backup. I move to eigrp for the isdn solution. I configured a ACL with all the remote subnets on the hub router. I then attached this to to a route-map and prepend these routes twice. For good measure I also set-weight for all the remote subnets to 40000. After testing it worked like a dream!!

[maher]

Hi Delroygordan,

How do you implement that? Mind if you could tell us how go you go about it? Perhaps some technical documents..

thanks in advance.

maher

[romccallum]

Folks, this is typical working when using OSPF. Using OSPF the down bit is set on LSA (not all of them but I dont need to go down that far). Because the router is redistributing the static routes into OSPF the PE router shall receive the routes via the mpls cloud from that redist point. It will then get them back from the original PE-CE but these will never come in. You have GOT to configure sham-links between any area (PE)s that have a backdoor between them. If the ISDN line is using OSPF then what happens is that the routes across the ISDN line appear as "O" routes and the routes from the PE-CE conenction appear as "IA" routes. Hence the ISDN line is the preferred path. Read up on sham-links as they go into the real detail of why this happens. Once you get used to what is happening it all rather makes sense. :-)

[rosaho]

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