we have 2x Juniper QFX as access switch (In Virtual chassis mode) and we have 16x Rack, we have 1x 10Gbps sfp+ uplink to each juniper so each rack has 2x 10g towards 2x Juniper qfx access switch and then we connect our nexus 3k to this qfx and we are doing layer3 routing on these 3k switch , but due to latencies and some other issue we want to bypass our access switches (that juniper qfx) and connect our top of rack switches to these pair of nexus 3k (they are vpc mode) so i want to know if we do this action does it impact on 3k switch ? because that 3k should handle traffic from different port (top of rack uplink) instead of single lacp towards qfx , so i imagine this wrongly and i can move my top of rack uplinks to this 3k without any worry ?

Current config: enter image description here

Aim: enter image description here

  • Do you have a pair of QFX in each rack? How are you planning to provide enough ports on the 3k? Juniper QFX have sub-microsecond latency, so you won't gain much there unless there's congestion. You should add a network diagram and connectivity details to your question, possibly you've got another problem.
    – Zac67
    Dec 12, 2020 at 11:19
  • i have a pair of n3k so i have 1x ex4200 as top of rack in each rack and first 10g of ex4200 will connect to first n3k and second 10g of ex4200 on the same rack will connect to second n3k and yes i have enough ports, because i need 15-16x Ports on each N3k
    – Blackmetal
    Dec 12, 2020 at 11:21
  • If the QFXes are actually EX4200s then please edit your question to better detail your setup. Currently, it's quite confusing.
    – Zac67
    Dec 12, 2020 at 13:38
  • Take the time to draw a diagram. This really isn't a Q&A situation; you're asking for people you don't know to consult on your network design. I suggest you make it easy to understand your current and proposed topology and clearly list what are your actual questions; otherwise you may get answers based on an incorrect understanding of your needs. Dec 12, 2020 at 13:55
  • look at i.imgur.com/tBcM3hH.png this is current topology, pair of qfx is doing only l2 and pair of n3k is only doing routing (bgp, ..) now for some reason i want to do this diagram: i.imgur.com/ck7lOdJ.png so pair of n3k is doing l2 and l3 at the same time, for l2 feature i do not use any special feature there are port-channel per top of rack switch and switch port access vlan 1,2,... just it, so if i do second topology does it impact on n3k switch performance, or it does not it?i guess there is no impact , it just receive traffic from different ports instead of 1x port-channel
    – Blackmetal
    Dec 12, 2020 at 15:39

1 Answer 1


Collapsing the L2 distribution layer onto the Nexus 3ks should work.

You might also want to provide L3 resiliency by configuring HSRP on the Nexus. Depending on bandwidth demand, you could use two HSRP gateways, one for each switch, and fail that over to the other one.

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