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How to attract traffic to one wan router over another OSPF Q
Imagine a remote site - call it Dallas - with two WAN routers. Router WAN1 connects to the data center in Denver over a 1Gbps circuit and router WAN2 connects to the data center over another 1Gbps circuit. All the routers are participating in OSPF.
[core-sw1]---[WAN1]~~~~ckt
[core-sw1]---[WAN2]~~~~ckt
The Dallas site has network 172.25.0.0/16 and currently that gets advertised such that traffic to Dallas goes equally over WAN2 and WAN1. I would like a specific subnet say 172.25.200.0/23 to prefer ckt2 unless ckt2 goes down then it would use ckt1. What would I do in OSPF to color the route for 172.25.200.0 so that the data center prefers sending via ckt2?
Thank you.
[core-sw1]---[WAN1]~~~~ckt
[core-sw1]---[WAN2]~~~~ckt
The Dallas site has network 172.25.0.0/16 and currently that gets advertised such that traffic to Dallas goes equally over WAN2 and WAN1. I would like a specific subnet say 172.25.200.0/23 to prefer ckt2 unless ckt2 goes down then it would use ckt1. What would I do in OSPF to color the route for 172.25.200.0 so that the data center prefers sending via ckt2?
Thank you.
Asked:
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1 Solution
LVL 8
Do you have any diagram of your network? There's many method to do so, but I'd love to analyze your thought with more detail if I see your diag.
I've attached a very simplified version. The two WAN router at each site are connected to each other and connected to a corresponding WAN router at the remote site. The routers are transmitted via OSPF. If I wanted Denver networks to choose say circuit 2 for 172.25.200.0 - what would I do to get that path favored? I could I suppose go onto the Denver router connected to ckt and use a static route with the lower metric and being favored for being more specific. But there's got to be an OSPF way to do this. It's just been too long since I watched the training on this.
ScrnGrab2673-171018-20.02.jpg
ScrnGrab2673-171018-20.02.jpg
Simplified topology will not help. For OSPF traffic engineering all data need to be provided.
Generally, inside of single area there is no traffic engineering except manipulating link cost (or without using Traffic Engineering (TE) Extensions to OSPF Version2 - Opaque Link State Advertisements - that needs to be supported by routers). Changing cost and getting proper result may require to change default reference bandwidth on all OSPF routers (if all links have low cost (e.g 1) there is no other way to make lower cost path.
Generally, inside of single area there is no traffic engineering except manipulating link cost (or without using Traffic Engineering (TE) Extensions to OSPF Version2 - Opaque Link State Advertisements - that needs to be supported by routers). Changing cost and getting proper result may require to change default reference bandwidth on all OSPF routers (if all links have low cost (e.g 1) there is no other way to make lower cost path.
Thanks. I also found a good explanation and example here:
https://learningnetwork.cisco.com/thread/57487
https://learningnetwork.cisco.com/thread/57487
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