Symptom

C9800-L-F does not support auto negotiation for the use of SFP GLC-SX-MMD. This is an expected behavior due to HW limitation even though you can configure "negotiation auto" on the C9800 interface. Catlyst9500switch# show interfaces TenGigabitEthernet 1/0/3 TenGigabitEthernet1/0/3 is down, line protocol is down (notconnect) <<-- Link should be shown as down, "not connect" on the connected Catalyst switch. Catlyst9500switch# show run interface TenGigabitEthernet1/0/3 switchport trunk native vlan 10 switchport trunk allowed vlan 10,12 (no speed nonegotiate) <<-- speed negotiation : Enabled (Please be aware, Catalyst switch configuration is tricky.) switchport mode trunk C9800LF# show interfaces TenGigabitEthernet 0/1/0 TenGigabitEthernet0/1/0 is up, line protocol is up <<-- C9800 may show the link is up/up.However it's not. C9800LF# show run interface TenGigabitEthernet0/1/0 switchport trunk native vlan 10 switchport trunk allowed vlan 10,12 switchport mode trunk negotiation auto <<-- speed negotiation : You can configure this line however it does not have any effect. Auto negotiation is not supported.

Conditions

C9800-L-F, SFP Module : GLC-SX-MMD

Workaround

disable speed negotiation on connected switch. Catlyst9500switch# show run interface TenGigabitEthernet1/0/3 switchport trunk native vlan 10 switchport trunk allowed vlan 10,12 speed nonegotiate <<-- speed negotiation : Disabled switchport mode trunk

Further Problem Description