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  • 1.  QFX 3500 MLAG

    Posted 06-15-2020 07:22


    Recently we used Arista with MLAG feature for redundancy and now are have in mind to use 2x QFX 3500 for one of our pop sites, can any one explain me how can i configure mc-lag between this 2x qfx3500 ?

    i have 5 rack and every rack has ex4200 as top of rack switch and one of the ex4200 10gb port is connected to qfx3500 #1 and other one is connecte to qfx3500 #2


  • 2.  RE: QFX 3500 MLAG

    Posted 06-15-2020 07:29

    QFX3500, I did not know anyone still using these 😁 QFX3500 can support either MC-LAG (equivalent to Arista MLAG) or VC.  Both will allow the 2 x QFX3500s to look like one switch to external connections.  VC is generally easier config, but single control plan (Master RE and Backup RE).  For MC-LAG each node runs its own control plane as independant REs.


    Good luck.

  • 3.  RE: QFX 3500 MLAG

    Posted 06-15-2020 08:07

    yes we have them in stock,

    but when we configured mlag in arista both switches works in active-active mode so every rack has 20gbps lacp capacity but as i understand with vc in juniper the second switch will act as backup and i have 1x 10g capacity , so i think i should go with mc-lag in juniper right?

    is there anyguide for this on qfx3500 ?

  • 4.  RE: QFX 3500 MLAG

    Posted 06-15-2020 08:57

    Not true about VC.  Since the VC acts like 1 switch, a multi-interface LAG is created from [in general] different members of the VC and all are active members of a single LAG.  Think of this as a chassis with multiple modules where you create a LAG than spans across the modules.  All interfaces are active, so you have link level redundancy and HW module failure redundancy.  You VC LAG will be all active members so you'll get 2 x 10G throughput.


    LAG will use a similar algorithum as MC-LAG as how to pick link on which traffic is sent.


    I doubt there is a specific document for MC-LAG for QFX3500, but there should be a generic MC-LAG doc using some product, for which the configuration/set-up should be the same.  One concern maybe that QFX3500 does not support any current code, so some of the newer MC-LAG capabilities and improvements may likely not be there.  I've never done MC-LAG with QFX3500, so I might suggest VC might be a better and safer option.

  • 5.  RE: QFX 3500 MLAG

    Posted 06-15-2020 09:06

    we have in mind to use these switch just as layer 2 switches and we do not want to have any bgp, ospf or other routing protocols on it, so running VC on them needs any special licenses?

    as i know there is no licenses installed in this switches.


  • 6.  RE: QFX 3500 MLAG

    Posted 06-15-2020 09:39

    For those switches no license needed for VC.  Again, I would suggest this is best path to follow for such an old switch.  You do know that these switches go End of Support 5/1/2021, yes?



  • 7.  RE: QFX 3500 MLAG

    Posted 06-15-2020 09:51

    thank you fir guide me in best way and yes i know about eol and eos .

    so for confirmation i can use qsfp ports and connect  both qfx3500 together and create VC and then every top of rack switches can have 2x 10g(20gbps) total throughput and no license needed for VC on qfx3500 ,r ight?


  • 8.  RE: QFX 3500 MLAG
    Best Answer

    Posted 06-15-2020 10:01

    Yes, should work, no issue.  I might suggest you run this by your local Juniper contact/partner/etc., if you have one.