Brocade ICX6450-C12-PD SFP ports stay down: the C12 only does 1G while the peer ICX6450-24P defaults to 10G

The two SFP ports (F1/F2) of a Brocade ICX6450-C12-PD, licensed for 10G, would not come up with either a Brocade 1000BASE-LR SFP (33211-100) or 10GBASE-SR modules over a 5 m single-mode patch to an ICX6450-24P. show media saw the transceivers but the interface reported GigabitEthernet1/3/1 is down, line protocol is down.

• Hardware: Brocade ICX6450-C12-PD, Brocade ICX6450-24P
• Transceivers: Brocade 1000BASE-LR SFP 33211-100, 10GBASE-SR SFP+
• Form factor: SFP, SFP+

Symptoms / messages:

GigabitEthernet1/3/1 is down, line protocol is down
transceiver visible in show media but no link