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New Member

Problem with Trunking using GigaStacks

Hi,

I have 1 3550 and 2 2950 switches connected using a GigaStack Cable using the below setup

3550 (Gigastack to 2950-SW1 and 2950-SW2 using Port Gi0/2)

2950-SW1 to 2950-SW2 using GigaStack(Ports Gi0/1 on both)

I somehow cannot seem to configure a 802.1q trunk on any of the interfaces. DTP doesn't seem to work and even forcing the interfaces to be trunks, they still don't show up in the command "show interfaces trunk".

Is there any special config required for this ?

9 REPLIES
Hall of Fame Super Bronze

Re: Problem with Trunking using GigaStacks

As the only encapsulation available on those switches is 802.1q, you don't need to configure it since that's the default.

You only need to configure it if you have another encapsulation option such as ISL.

You've executed the correct command to verify if you are indeed running 802.1q, which you are.

HTH,

__

Edison.

New Member

Re: Problem with Trunking using GigaStacks

Hi,

That is the problem. Why am I not seeing the interfaces operating in Trunking Mode (Even when they are forced to be)? This config works fine when not using GigaStack.

3550 actually has both ISL and 802.1q and I configured it to use 802.1q to match the other switches.

\\ Naman

Hall of Fame Super Bronze

Re: Problem with Trunking using GigaStacks

Please post the output from the following commands:

show inter switchport [module]

show run interface [module]

show interface [module] status

Thanks

__

Edison.

New Member

Re: Problem with Trunking using GigaStacks

Please see below.

+++++++++++++++++++++++++++++++++++

SW03_3550(3550 Switch using Gig0/2. Connected to SW04_2950 and SW05_2950)

================

interface GigabitEthernet0/2

description GIGA STACK

switchport trunk encapsulation dot1q

switchport mode dynamic desirable

end

===========

Name: Gi0/2

Switchport: Enabled

Administrative Mode: dynamic desirable

Operational Mode: static access

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: native

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 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

=================

sfmc-access-sw03# show interfaces gigabitEthernet 0/2 status

Port Name Status Vlan Duplex Speed Type

Gi0/2 GIGA STACK connected 1 a-half a-1000 1000BaseCX Gigastack

=================

Port Mode Encapsulation Status Native vlan

Gi0/2 desirable 802.1q not-trunking 1

++++++++++++++++++++++++++++++++++++++++++++

SW04_2950 (2950 Switch using Gi0/1- Connected to SW03_3550 and SW05_2950)

====================

interface GigabitEthernet0/1

end

====================

Name: Gi0/1

Switchport: Enabled

Administrative Mode: dynamic desirable

Operational Mode: static access

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: native

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: 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

========================

Port Name Status Vlan Duplex Speed Type

Gi0/1 connected 1 a-half a-1000 1000BaseCX Gigastack

========================

Port Mode Encapsulation Status Native vlan

Gi0/1 desirable 802.1q not-trunking 1

New Member

Re: Problem with Trunking using GigaStacks

<<<<< Continuation From Previous Messages>>

+++++++++++++++++++++++++++++++++++++++++++

SW05_2950 (2950 Switch using Gi0/1- Connected to SW03_3550 and SW04_2950)

======================

interface GigabitEthernet0/1

end

=====================

Name: Gi0/1

Switchport: Enabled

Administrative Mode: dynamic desirable

Operational Mode: static access

Administrative Trunking Encapsulation: dot1q

Operational Trunking Encapsulation: native

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: 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

=============================

Port Name Status Vlan Duplex Speed Type

Gi0/1 connected 1 a-half a-1000 1000BaseCX Gigastack

=============================

Port Mode Encapsulation Status Native vlan

Gi0/1 desirable 802.1q not-trunking 1

++++++++++++++++++++++++++++++++++++

Hall of Fame Super Bronze

Re: Problem with Trunking using GigaStacks

I see what you mean, you want to enable trunking with DTP.

It should work as desirable/desirable should form a trunk.

Have you tried updating the IOS version?

Can you post the output while configured with manual trunking?

__

Edison.

New Member

Re: Problem with Trunking using GigaStacks

Thanks for the quick response.

I can try to see, if we can upgrade.

Output with manual trunking is pretty much the same. The trunks are still 'Not' formed. So even with Trunking manually enabled on all specific ports the the Interfaces remain in Non-Trunking operational mode.

New Member

Re: Problem with Trunking using GigaStacks

mnlatif,

How did you end up fixing this issue. I have 3 3550's (cascading) running 12.2.44 SE6 ipservices and I am having the exact same issue...

Any help would be greatly appreciated.

Thanks in advance.

Mark

New Member

Re: Problem with Trunking using GigaStacks

In case anyone cares, the solution is here -

http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.2_25_see/configuration/guide/3550SCG.html

Page 291.

You must remove config from interface, then shut, config trunking then no shut.

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