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Load balancing on ISIS links between MX104's

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  • 1.  Load balancing on ISIS links between MX104's

    Posted 03-11-2020 00:48



    We are running an mpls network consisting of MX104's running ISIS in the core. We are providing mostly l2circuits and L3 VPN's to our customers. Each MX104 has 10G links between them. We are now planning on upgrading to have 20G between each MX. Since we want to achieve load balancing, what type of configuration is best practice? Is it to run LAG with LACP on the 2 x 10G ISIS links? Or should we just use two point-to-point links and load balancing will occur by default hash-key? We don't have any hash-key configured in forwarding-options as of today. Any recommendations on what we should use?


    Someone told me that LACP should be avoided since there could be problems if CPU is busy. However the CPU utilization are running at 95% Idle mostly and we don't have any large routing-tables or similar that would cause pressure on the CPU. 



    Thanks in advance.




  • 2.  RE: Load balancing on ISIS links between MX104's
    Best Answer

    Posted 03-11-2020 08:02

    Hi Reccy,


    LACP is a very light weight program it should not have much CPU penalty. Specially, in new release the ppm on PFE takes care of periodic LACP PDU so RE would come into picture only during LACP initialization.


    For default hash calculation and available option please refer following article.


    KB27288 and KB24339: This article explains how to verify the fields used in hash-key computation for load-balancing on Trio line cards.



    PS: Please accept my response as solution if it answers your query, kudos are appreciated too!




  • 3.  RE: Load balancing on ISIS links between MX104's

    Posted 03-24-2020 01:51

    Thanks Vishal! It sounds like it is safe to use LACP then. I will go ahead and configure that.


    Regarding hash calculation I was hoping to get some recommendation on best practice given the type of services running in our network. I can't open the two first links though. Maybe those explain this?