I have a cisco catalyst 3560G-48TS switch that is connected via the SFP port module (GLC-SX-MM) multimode fiber to a Cisco Catalyst 2560G -8 port managed switch which is uplinked also via a similar SFP fiber module (GLC-SX-MM) using multimode fiber. The link light on the 2960G (remote side) is lit and has no errors. I did some swapping of know good SFP modules and no change I connected another remote uplink to said SFP port and link light appears, however when connected to the 2960G switch no link light however i still have a stable trunk connection. Also the web interface of the 3560G shows a lit port on the visual of the switch. Both sides are trunked using the following:
Catalyst 3560G Port config:
interface GigabitEthernet0/51
description Building 5 Uplink-Location 1299
switchport trunk encapsulation dot1q
switchport mode trunk
2960G Port config:
interface GigabitEthernet0/8
description Core Uplink-New
switchport trunk encapsulation dot1q
switchport mode trunk
What can be causing this as a tech mistakenly thought it was down and started diagnostics thinking the link was down causing a unneccessary disconnection of the link as the link was in fact up and operational.
