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No SFP link light but trunk operational with no errors.

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.


Hi @richardsk,Is this a new

Hi @richardsk,

Is this a new switch? Does it happen if you connect any link to it?

As I see, It seems like a hardware issue. Maybe the LEDs of the port are damaged.


Martin, IT Specialist


Hi Rich,Probably the LED is

Hi Rich,

Probably the LED is dead.
Only probable reason considering the uplink is good

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