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New Member

Strange Trunking issue

I am working on configuring switches with VLANs and trunking these switches using dot1q encapsulation. I configured two ports from two switches as trunk ports properly, but when executing a sho cdp neigh or trying to ping one another, there is no link between the two. Below, I am listing the output of both ports from both switchs.

What seems to be the problem that is preventing the establishment of the trunk?

Thanks in advance,

sK

-----------------------------------

Name: Gi0/3

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: dot1q

Negotiation of Trunking: Off

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 private VLANs: 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

Name: Gi0/4

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: trunk

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: dot1q

Negotiation of Trunking: Off

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 private VLANs: 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

7 REPLIES
Hall of Fame Super Bronze

Re: Strange Trunking issue

Please post the output from typing

show int trunk and show int status from both devices.

__

Edison.

New Member

Re: Strange Trunking issue

NY-SW1#sho interfaces trunk

Port Mode Encapsulation Status Native vlan

Fa0/48 on 802.1q trunking 1

Gi0/1 on 802.1q trunking 1

Gi0/4 on 802.1q trunking 1

Port Vlans allowed on trunk

Fa0/48 1-4094

Gi0/1 1-4094

Gi0/4 1-4094

Port Vlans allowed and active in management domain

Fa0/48 1,20,30,40,50

Gi0/1 1,20,30,40,50

Gi0/4 1,20,30,40,50

Port Vlans in spanning tree forwarding state and not pruned

Fa0/48 1

Gi0/1 1,20,30,40,50

Gi0/4 1,20,30,40,50.

NY-SW1# sho int status

Gi0/4 connected trunk a-full a-1000 10/100/1000BaseTX SFP

----------------------------------------------

Sac-SW2#sho interfaces trunk

Port Mode Encapsulation Status Native vlan

Gi0/3 on 802.1q trunking 1

Port Vlans allowed on trunk

Gi0/3 1-4094

Port Vlans allowed and active in management domain

Gi0/3 1,20,30,40,50

Port Vlans in spanning tree forwarding state and not pruned

Gi0/3 1,20,30,40,50

Sac-SW2#sho int status

Gi0/3 connected trunk a-full a-1000 10/100/1000BaseTX SF

Hall of Fame Super Bronze

Re: Strange Trunking issue

Well, trunking is up and forwarding the Vlans.

You mentioned you are unable to ping from switch to switch, can you post the output from typing

show vtp status, show vlan and show ip interface | ex una from both switches.

__

Edison.

New Member

Re: Strange Trunking issue

Output in attched file.

Hall of Fame Super Bronze

Re: Strange Trunking issue

Couple of comments from the output you posted:

1) VTP

Switch 1 Configuration Revision : 13

Switch 2 Configuration Revision : 0

The VTP mode on switch 1 VTP Operating Mode : Server

The VTP mode on switch 2 VTP Operating Mode : Client

Both switches have the same VTP domain name SKTECH.

Question, did you create the Vlans manually on switch 2 and then changed the VTP mode to client ? If the client switch inherited all Vlans from the server switch, the configuration revision will be the same.

Change the domain name in the client switch to something else, change it back to SKTECH and bounce the trunk interfaces with shut and no shut.

2. I ask for the show ip interface | ex una output, it should display only interfaces with IP on it. You mentioned you can't ping from switch to switch, right ? Then the switches must have IP on them. Unless you referred to pinging from workstations connected on Switch1 to workstations connected on Switch2. Which is it?

New Member

Re: Strange Trunking issue

The answer to your first qustion is yes. Sac-SW2 was connected to a different VTP domain and then I connected it to NY-SW1 and trunked the porst, set the mode to client. As for your other questions, the attached file has all the output you asked for.

Thanks much!

sK

New Member

Re: Strange Trunking issue

Ed.. Thganks for all help. As it turns out that the GLC-T on Sw2 was bad. Once I replaced it with a new one, everything worked as they should..

Thanks again,

sK

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