7.2 Routing Policy

This task asked for providing routing policy on the PE`s R8 and R7 using Communities tag to influence routing decission towards R9 routes ( the CE ) inside the MPLS cloud .

After the policy has been successfuly applied R10 can reach R9 routes through R8 instead of R7  .

 

However, R 10 does not retain the new LOCAL PREF value assigned by R8 because the prefix of R9 is moving to EBGP peer R10.

 

MY question is , in the real word  can we use the community signaling method to influence the inbound traffic even if we are peering with two different providers ??

thanks

 

Comments

  • MartinlMartinl ✭✭✭

    i think so,  MED can be use but not if u have 2 different AS neighbors. so, community tags is what u have left if u are peering with two different providers.  

    Most if not all ISP will accept your community tag and have set up mapping for those so that traffic engineering becomes doable.

  • peetypeety ✭✭

    MY question is , in the real word  can we use the community signaling method to influence the inbound traffic even if we are peering with two different providers ??

    Got dice? It's an absolute <insert a word here>shoot, for both MPLS and DIA. Some give great support, some give limited support, and I've even seen one DIA that appeared to intentionally strip all communities off, including well-known. Others refuse to accept MED.

  • Thats the case that i have that even i use the communities to signal a local pref or MED for other values , then when the route leaves the AS ( provider next to my AS ) the attributes will be reset to it default ( local PREF 100 , and MED 0 ) or stripped off.

     

     

     

     

     

     

  • MartinlMartinl ✭✭✭

    what is DIA ?  ISP ? not all will stripped or not communities; don't you ned some kind a agreement with ISP?

  • What Martin wrote is true - you can't control the incoming path - you can use community values or AS-Path prepending to REQUEST a particular path, but each ISP can have its own policies that may or may not respect your request.

    MED (or any other community value) is not necessarily sent/preserved betwen ISPs, so community values will not work unless you have an agreement with both ISPs that they will share your community values and will honor the community values in their path selection policy.

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