MPLS TE LOADSHARING

[romccallum]

Hi,

I cant find any decent documentation on this and unfortunately loaned Erics book to someone else (damn). Anyway. Is there any decent documentation explaining how you can have two tunnels to the same destination but use different paths and loadbalance over the tunnels. IGP is OSPF. I take it to put these tunnels into OSPF we are in forward adjaceny area which is fine and the tunnel cost would be OSPF cost. Another thing is when we do this we would use dynamic bandwidth allocation and also look to be able to have the traffic from any source to use this tunnel.

Any takers ?

[Harold Ritter]

Robert,

FA will attract traffic from upstream sources to the headend router. If you have two or more tunnels to the same tailend, all destinations downstream to the tailend should be loadbalanced over the multiple tunnels by default.

Hope this helps,

[romccallum]

how you mate - thanks for the quick reply. The key here is that the tunnel tail ends are going to be different routers. Also over different paths. They will be from the same head end however. I am going to be labbing it up on Monday but I am worried about assymettric routing.

[Harold Ritter]

Robert,

I had a chance to look at this issue and found that loadsharing to a given destination between two tunnels to different tailends is only possible if the smallest IGP cost to the two tunnel tailends are equals.

Hope this helps,

[romccallum]

thanks for that Harry - I mocked it up in the lab and with the IGP being the same it worked fine as you suggested - It was quite odd when the IGP costs werent the same - made for some nice debugging etc. Anyhow job done, tested, designed, implemented - now the hard part - get the support team to be able to debug it when it all goes pear shaped ;-)

[Harold Ritter]

Rob,

I came across the same issue again recently and I ran another quick test. It is indeed possible to loadbalance between two tunnel to two different tailends even if the IGP cost to the tailends is different.

The only thing you need to do is adjust the metric on the tunnel to the tailend to the higher IGP metric to be the same as the other tunnel.

Sorry for the confusion,