Help*Problem Trunking between Catalyst 2950 switches.

Answered Question
May 15th, 2012

Hi All,

I am new to Cisco and have setup a small lab as per CBTNuggets. Everything was going well until I introduced a second switch to create a trunk. Now I cannot ping between my two switches. Both show operational mode as down:

SWITCH1#show interfaces f0/12 switchport

Name: Fa0/12

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: down

Administrative Trunking Encapsulation: dot1q

Negotiation of Trunking: On

Access Mode VLAN: 1 (default)

Trunking Native Mode VLAN: 1 (default)

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 encapsulation: dot1q

Administrative private-vlan trunk normal VLANs: none

Administrative private-vlan trunk private VLANs: none

Operational private-vlan: none

Trunking VLANs Enabled: 1

Pruning VLANs Enabled: 2-1001

Capture Mode Disabled

Capture VLANs Allowed: ALL

Protected: false

Appliance trust: none

And There doesn't seem to be any vlans enabled to trunk. See Below

SWITCH1#show interface f0/12 trunk

Port        Mode         Encapsulation  Status        Native vlan

Fa0/12      on           802.1q         not-trunking  1

Port      Vlans allowed on trunk

Fa0/12      none

Port        Vlans allowed and active in management domain

Fa0/12      none

Port        Vlans in spanning tree forwarding state and not pruned

Fa0/12      none

I have tried to allow all vlans or vlan 1 specifically and the output of the above doesn't seem to change.

I am wondering if there is something in the config-register that is preventing trunking, but I don't really know enough yet!

The output of my second switch is identical to this one, the only difference is that I have it configured as a vtp client.

Hope someone can help.


I have this problem too.
0 votes
Correct Answer by rettuc_ccnp about 2 years 10 months ago

Hey craig,

I'm going to guess that you are using a straight through cable instead of a cross-over cable.
Switch to a cross-over cable and everything should come up

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Overall Rating: 5 (1 ratings)
Correct Answer
rettuc_ccnp Tue, 05/15/2012 - 14:17

Hey craig,

I'm going to guess that you are using a straight through cable instead of a cross-over cable.
Switch to a cross-over cable and everything should come up

Craigie750 Tue, 05/15/2012 - 15:10

I thought it was a cross-over, but looking at it now it doesn't look like it. I will get a hold of a cross-over, and try that.

Let you know how it goes.

Craigie750 Tue, 05/15/2012 - 15:10

ps Thanks.

Craigie750 Wed, 05/16/2012 - 11:16

Spot on rettuc_ccnp, found a crossover at work today and is now working! I did get a couple of cables with my lab and presumed they were crossover, never really checked.



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This Discussion

Posted May 15, 2012 at 12:10 PM
Replies:4 Overall Rating:5
Views:1244 Votes:0
Categories: Switches

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