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New Member

3560 switch, trunk issue

3560 connected to 4550 via SFP trunk


Gi0/3     connectedto G6/1   connected    trunk      a-full a-1000 1000BaseSX SFP

interface GigabitEthernet0/3

description connectedto G6/1

switchport trunk encapsulation dot1q

switchport trunk native vlan 500

switchport trunk allowed vlan 100,200,300,400,500,800

switchport mode trunk

no ip address

The link light on the 4550 Gi6/4 is solid green, but

The link light on the 3560 Gi0/3 goes from amber to green about once a second.

I haven't tried on all ports, but on a couple of the access-ports the connection to the rest of the network (through the trunk) is slow or non-existent (times out).

I originally had it on 3560 port Gi0/2 and the console was logging "Gi0/2 LinkDown | Gi0/2 Link Up" messages (i'm guessing once every 15 seconds, but more random).  Since I moved the trunk to Gi0/3, the console messages do not show up, but the link light still goes from green to amber.

Any ideas?  I've taken out the fiber, doesn't look dirty.  Canned Air cleaned.

Any help would be appreciated.


Cisco Employee

Re: 3560 switch, trunk issue

Have you tried swapping SFP?



Hall of Fame Super Gold

Re: 3560 switch, trunk issue

What's the distance between both appliance.  Sounds like the distance is further than the SFP can support.

New Member

Re: 3560 switch, trunk issue

Swapping SPF?

I'm sorry, I'm not that familiar with SPF.  What do you mean?  Crossing the pairs?

The 4500 is in the basement, the 3560 is on the 2nd floor.  It has worked fine this way for about four years now.

Think it could have gone "bad"?

Cisco Employee

Re: 3560 switch, trunk issue

Maybe I should rephrase it. Have you change your fiber transceiver (SFP - small form pluggable).



New Member

Re: 3560 switch, trunk issue


Pl closely monitor the speed mismatch or spanning tree flapping or foword/blocking this port

show interface gi0/3

show spanning-tree vlan


krishna kumar

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