So to preface, I'm not a network engineer but am somehow in charge of getting our juniper QFX5200-48y configured. The goal is to get our FS brand SPF28's and QSFP28's to talk to each other on the juniper switch, so far have been able to configure the regular SFP28 ports to use 25g speeds but no luck in getting the 100g to breakout into 4x25g. QSFP28 to QSFP28 works just fine. Have tried several methods now with no luck and am at my wit's end. Googling, I was able to get one of the 4 channels (et-0/0/48:0) to talk to a singular SFP28 but oddly not the other 3 channels. I would be supremely grateful to anyone who could shed some light on this topic or at least point me in the right direction. Much appreciated!


  • What do you mean by “talk to”, do the interfaces have IP addresses or do you mean that both ends linked up? Would be helpful to see “show configuration” from the QFX. May 15 at 0:23
  • They won't link up at all. To be clear this switch hasn't been deployed. I don't have access to it right now but will either sometime this weekend or monday. The interfaces don't have ip addresses. Sorry if that doesn't make any sense, I'm kinda trial-by-fire-ing this thing. Thanks
    – girafferan
    May 15 at 1:24
  • Zac is correct, no channelization of the 100G links. May 15 at 13:11

QFX5200-48Y Channelization

When one of the 6 QSFP28 ports are configured for 40-Gigabit Ethernet and a 4x10G breakout cable is detected, the system converts the port into 4 independent 10-Gigabit Ethernet ports. Channelization is not supported on the 48 SFP28 ports.


As it seems, that switch doesn't support 4x 25G breakouts, just 4x 10G. A -32C would.

  • So to clarify, the SFP28 ports not being able to channelize into 4x25g is what's preventing the link or is it the QSFP28 ports that don't like to be split up that way? Thanks again for everyone's patience.
    – girafferan
    May 15 at 14:24
  • The breakout needs to happen at the QSFP28 (or QSFP+) port. The SFP28/+ ports connect normally.
    – Zac67
    May 15 at 16:21

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