Branfarm1,

1- There is no explicity trunk encapsulation command in this ios version. Only works with the dot1q by default

2- I have made a compare with the commands sh int gig0/x switch port

Can you check in order to see if there is someting wrong:

From the 2960:

L24SW-02#sh interfaces gigabitEthernet 0/1 switchport

Name: Gi0/1

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: dot1q

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Administrative Native VLAN tagging: enabled

Voice VLAN: none

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Administrative private-vlan trunk native VLAN: none

Administrative private-vlan trunk Native VLAN tagging: enabled

Administrative private-vlan trunk encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk associations: none

Administrative private-vlan trunk mappings: none

Operational private-vlan: none

Trunking VLANs Enabled: ALL

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL

Protected: false

Unknown unicast blocked: disabled

Unknown multicast blocked: disabled

Appliance trust: none

From the C3508:

L22BB-01#sh int gigabitEthernet 0/4 switchport

Name: Gi0/4

Switchport: Enabled

Administrative mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: dot1q

Negotiation of Trunking: Disabled

Access Mode VLAN: 0 ((Inactive))

Trunking Native Mode VLAN: 1 (default)

Trunking VLANs Enabled: ALL

Trunking VLANs Active: 1,10-12,20,25,100-102,200,300,400-405,500,510,555,600,

700,900-908,914,920,922,923,939-969

Pruning VLANs Enabled: 2-1001

Priority for untagged frames: 0

Override vlan tag priority: FALSE

Voice VLAN: none

Appliance trust: none

From the C3548

L24SW-01#sh int gigabitEthernet 0/1 switchport

Name: Gi0/1

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: dot1q

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

Administrative private-vlan host-association: none

Administrative private-vlan mapping: none

Operational private-vlan: none

Trunking VLANs Enabled: ALL

Pruning VLANs Enabled: 2-1001

Protected: false

Unknown unicast blocked: disabled

Unknown multicast blocked: disabled

Voice VLAN: none (Inactive)

Appliance trust: none

So when you say the link between the two switches isn't working does that mean that the trunk never actually forms and the link shows down on one side?

Exactly it is like there is no fiber connecting them.

It is equal as I remove the fiber.

Hmm... that's an interesting one. Have you started off with the most basic of basics - tried a different piece of fiber, different GBICS or SFP's, different slots?

Yes already tried this.

Replaced the Fiber patch cord, the gbic and changed the port, but no joy

Well, I wish I could be more help, but it sounds like we'll need to get someone with more technical troubleshooting skills involved. This is starting to appear like it's more than just a configuration issue.

On a related note, I've had this problem in the past with fiber connections between 4507's and 3020 Blade switches. I was never able to get the link to work though, so I had to switch it over to a copper connection. I'm interested to find out what the solution ends up being.

can you send me "sh vlan brief or show vlan" on the C3508

One thing to check on gig stuff is the flow control. I normally only have a issue between cisco and non cisco stuff.

If the ports are in a up status you may want to check and see if you see CDP neighbor or spanning tree active on vlan 1.

If these are up the next to check is for a VTP issue. When you force the ports to trunk you they will come up even if the VTP domain does not match but they will not exchange any vlan information.

Tdrais,

What does it mean if the one end of the link shows as down? That's the problem I had -- one end of the link showed up, while the other end showed down. I tried multiple cables, GBIC's, ports, etc.

Hi

It me have something to do with the

Administrative Native VLAN tagging: enabled

Settings on the 2960.

Try to change it to no native vlan tagging (default).

Willem

I have the same problem a year ago,

what i have did is specified the speed and the duplex on the interfaces. Although this would not required but helped me to bring the link up.

secondly try by removed the trunk configuration on each switch.