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New Member

redundancy & load sharing between 2 links

I have 2 pairs of Cisco routers connected to a remote office via 2 separate leased lines running OSPF.

Under normal condition, I want the traffic of voip , SDLC & packet destined to to traverse on the 1st link

whereas the rest of traffics (destined to /24 & /16) to go through the 2nd link.

(load sharing)

In the even of one the links is not available, the other link will back it up , i.e all traffics will traverse through the only available

link. (redundancy)

Kindly advise how could I configure them in order to meet above requirement.

Thank you

  • Other Network Infrastructure Subjects

Re: redundancy & load sharing between 2 links

There are three common ways to attack this challenge: defining longer prefix routes favoring the preferred routes, weighting the routes advertised based on the advertised prefix, and using policy routing to override the routing tables. Since you are using OSPF, the first option won't work and the second is tricky to set up correctly, so your only real choice is probably policy routing.

In most cases, you will need to use policy routing anyway for the return traffic, unless the source of the traffic can also be distinguished by IP address. When setting up the policy routing, don't forget to provide for fallback to the alternate link in case of primary link failure.

Hint: remember that you need to detect link failure before you can react to it, this is automatic as long as all routing decisions are based on IP addresses learned via OSPF.

Good luck and have fun!

Vincent C Jones

New Member

Re: redundancy & load sharing between 2 links


thank you for reply, i manged to configure the routers to auto detect & fallback to the alternate available link but the traffic that originally traversed through the failed link blocked by the access-list.

Would appreciate if somebody could enlighten me by providing some samples.


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