Load sharing based on link congestion

Discussion in 'Cisco' started by jlamanna, Jul 19, 2009.

  1. jlamanna

    jlamanna Guest

    Hi,
    Is there a way to have a cisco router fill up 1 link and then
    "overflow" to a second parallel link?
    The reason I don't want equal cost or round-robin is this situation:

    I have a high reliability link A with bandwidth B_a and a lower
    reliability link B with bandwidth B_b.
    B_b > B_a. However, I want as much of the A link used as possible
    because it is the high reliability link.
    Extra usage should "spill-over" into link B.

    Is this possible?

    Thanks.
     
    jlamanna, Jul 19, 2009
    #1
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  2. The Cisco 10000 series offers a dynamic bandwidth ratio feature that
    appears to perform a similar function, but I doubt that's the platform
    you're running. :)

    If you're running MPLS, I believe MPLS Traffic Engineering features
    might be utilized to accomplish your goal.
     
    fugettaboutit, Jul 19, 2009
    #2
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  3. jlamanna

    Trendkill Guest

    L2 load balancing can work this way (i.e. etherchannel), but generally
    load balancing at layer 3 is round robin on packet or flow, neither of
    which would fill up a pipe and then spill over into another. Perhaps
    you could do policy based routing and put your heavy hitters on one of
    the links and split it that way.
     
    Trendkill, Jul 19, 2009
    #3
  4. jlamanna

    brink Guest

    The routing protocols and the L3 forwarding do not normally take line
    utilisation into account so that won't work. The best route(s) is(are)
    in the routing table and line utilisation is not a factor because it
    could cause instability. Policy based routing doesn't know about it
    either.

    I suggest you have a look at an output policy for your favoured link.
    It should be possible to prioritise traffic, ratelimit it to line
    speed and send remaining traffic to the next hop at the other end of
    the 2nd line. Depending on speed and hardware used you may run into
    practical limitations like max throughput and getting (close to) 100%
    load on the reliable line. You''ll have to do this in both
    directions.
     
    brink, Jul 20, 2009
    #4
  5. jlamanna

    theapplebee

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    As far as I know there are no solution for your inquiry.
    If you are using multiple links where is terminated one router on each end. You can us load-sharing per packet. I will make exact 50/50 traffic balance. It should be applied on both to affect.

    You can find BGP configuration on below article

    http://showipbgp.com/bgp-configurations/cisco.html
     
    Last edited: Sep 11, 2009
    theapplebee, Sep 8, 2009
    #5
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