ConnectX-4 Lx 25 Gbps Dual Port NIC, 2nd SPF28 Causes 1st SFP28 to Drop Briefly

Hi Everyone,

Wondering if anyone else has seen this behavior on ConnectX-4 Lx EN Dual Port SFP28 cards; we’ve seen it on 2 separate Dell R730 hosts where we have these cards installed (it’s safe to assume we’d see this behavior on all such cards/hosts we have deployed, but we only explicitly tested SFP28s on 2 hosts to date):

  1. We connect the first SFP28 transceiver into the dual port card, link comes up and auto-negotiates to 25 Gbps correctly.

  2. Connect second SFP28 transceiver into the same card, link for first transceiver goes down, then both links come up simultaneously and auto-negotiate to 25 Gbps.

  3. Disconnect either SFP28 transceiver, causes other active transceiver to go down briefly, then link returns and auto-negotiates to 25 Gbps.

Basically concern is having the connection/disconnection of a SFP28 causing the other SPF28 to lose its connection, causing a brief disconnect of the host or packet/data loss.

Looking for information/documentations to validate if this is the expected behavior, whether the card queues the packets during the brief downing of the the links, or if the packets drop.

Thanks in advance!