Connecting a UDM SE 10G SFP+ port to an Enterprise XG 24 SFP28 port: which DAC, and the mixed-speed limitation

The poster wanted to connect a UDM SE (10G SFP+) to an Enterprise XG 24 switch (25G SFP28) and asked whether an SFP+ DAC would work with the SFP28 port falling back to 10G, or whether an SFP28 DAC was preferable. The concern was whether the SFP28 cage would fall back to 10G with an ordinary SFP+ DAC and whether the two SFP28 ports could tehn still run one at 10G and one at 25G, given the switch's port-group speed rules.

• Hardware: Ubiquiti UDM SE, Ubiquiti Enterprise XG 24
• Transceivers: SFP+ DAC, SFP28 DAC
• Form factor: SFP+, SFP28, DAC

Symptoms / messages:

mixed 10G/25G port speeds