TNSR ECMP Algorithms?



  • Hi,

    We are considering TNSR for an upcoming project.

    Part of the requirements we have is to perform ECMP across a number of devices, but only hash on the source ip of each packet. I.e. we have a requirement that all traffic from source IP A always be sent to R1 on the other side.

    I know Linux out of the box cannot do this, its two configurable ECMP modes are 'L3' (which use SRC+DST IP) and 'L4' (which uses SRC IP + DST IP + SRC PORT + DST PORT + PROTOCOL.)

    I know certain vendor implementations allow selection of only Source IP for ECMP. Can anyone advise if this is possible with VPP / TNSR?

    Thanks.


  • Netgate

    Hi @cmooney,

    I am not sure it would work like that, we would let routing protocol decide on the best path(s) to take. However, to see if this is something that is configurable I would contact one of our sales engineers to see if it's possible.



  • It's not really to do with the routing protocol, it's really about the underlying packet forwarding engine.

    I can add two equal cost routes by creating two statics to different destinations, or those two equal-cost routes can be from OSPF, BGP etc. etc.

    The question is once there are two equal routes in the table how does the platform load-share between the two different next-hops.

    Thanks.


  • Netgate

    That is done via round-robin.



  • How do you mean round-robin?

    Per-packet round robin?


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