QSFP-100G-CU1M DAC link stays down between NCS55A2-MOD (IOS XR) and Catalyst 9500-48Y4C
The poster needs a 100GE link between a Cisco NCS55A2-MOD (NC55-MPA-4H-S MPA) and a Cisco Catalyst C9500-48Y4C using a QSFP-100G-CU1M DAC. Both platforms list the cable as supported, yet the link never comes up at the physical level. Because the Catalyst 9500 lacks 100G auto-negotiation (bug CSCvk07538), the poster disabled it on the NCS with 'interface HundredGigE 0/0/1/2' / 'no negotiation auto', to no effect. IOS XR 6.5.3, 6.6.3 and 7.0.2 were tested on the NCS with identical results. Per the NCS 5500 interface guide, 100G auto-negotiation is on by default on NCS 540 and NCS 55A2. The same DAC works NCS-to-NCS and Catalyst-to-Catalyst, so the poster susppects a platform interoperabiility problem.
- Hardware: Cisco NCS55A2-MOD with NC55-MPA-4H-S, Cisco Catalyst C9500-48Y4C
- Transceivers: QSFP-100G-CU1M
- Form factor: QSFP28, DAC
Symptoms / messages:
100G DAC link down between NCS55A2-MOD and Catalyst 9500
no negotiation auto has no effect
CSCvk07538 (no 100G auto-negotiation on Catalyst 9500)
same DAC works NCS-to-NCS and Catalyst-to-Catalyst
Comments 2
I've seen several auto-negotiation problems with this particular DAC. What software version are you running? Try enabling 'negotiation auto' on both sides.
I tried three different IOS XR releases and they all behave identically - the Catalyst side just can't negotiate at 100G. The only lever I've got left on the NCS is the 'no negotiation auto' knob, but I'm not sure it'll actually help.