Equal Cost Loadbalancing between 2 link from Same ISP

[Abdul_Salaam]

Hi All,

I need your help in identifying the issue why I am not able to do equal cost load balancing between 2 links using OSPF as routing protocol.

At My end I am using OSPF as routing protocol at lan side from both Site A and Site B and advertising lan subnet in OSPF using network command in OSPF process at ISP side they are using OSPF and then redistributing OSPF in BGP for MPLS link(link1) for Site A and sending routes to Site B and Vice versa and For the Express Connect link(Link2) they are using OSPF and sending route from Site A to Site B and Vice versa.

Now problem statement is that i am able to learn only routes from Express connect which ISP is running IGP (OSPF) and they are getting installed in Routing table. when I try to see the routes from MPLS link they are showing AS TYPE 5 routes in OSPF database but not getting installed in Routing table.

Now my requirement is to load balance between link1 and link2 at both location Site A and Site B.

Diagram updated for reference.

[Giuseppe Larosa]

Hello @Abdul_Salaam ,

OSPF internal routes are preferred over OSPF external routes this is why the link from Express Connect service are preferred.

Either you make arrangments with the ISP so that they use OSPF also on the other link (feasible if this link is an MPLS L3 VPN service but it may require an additional fee) in a way that makes the Type 5 routes to appear as O IA routes (but this cannot be enough because O routes are preferred over O IA, the ISP might need to use OSPF as PE-CE protocol + sham-link on PE routers)

Or you break the OSPF connectivity on the Express Connect and you use a different protocol ( that can also be a different OSPF process-id) so that you create same type external routes that can be compared.

This second option does not involve your ISP and it is in your hands if the Express Connect service is actually a L2 point to point service.

Edit:

if this is a lab I would go with using a different OSPF process -id on the Express Connect service .

You redistribute OSPF pid 12 into OSPF 20 and OSPF 20 builds the adjacency with ISP. You do the same on the other side and then you redistribute from OSPF 20 to OSPF 12 so that routes will be external.

External routes should be the same type ( O E1 are preferred over O E2) and the metric value should be the same.

Hope to help

Giuseppe

[Abdul_Salaam]

Hello @Giuseppe Larosa ,

Thanks for the response

Express connect is not Point to Point L2 Link, ISP is running BGP and OSPF separately in their environment not redistributing so we are learning routes from OSPF for Express Connect Link.

I will try your suggestion in lab which I have prepared for troubleshooting will get back to you post testing.

Abdul

[Deepak Kumar]

Hi,

I think here OSPF rules are making issues. OSPF says that O routes are preferred over O IA. It does not matter the cost.

[Abdul Salaam Khan]

Hi @Deepak Kumar ,

Yes OSPF rules is creating this problem  so any suggestion how to overcome this ?

Abdul