Tagging NATIVE VLAN (is the dafault or not) ?

ROBERTO TACCON · ‎02-24-2009

Hi to all,

can you check the following discussion about the "tagging native VLAN" and tell me if the tagging of the native VLAN is the deafult or not (on cat. 3560/37xx/45xx) with the latest IOS releases ?

http://www.networkworld.com/community/node/38732

If someone have a lab can do the following and paste the output :

1) configure a trunk between 2 switches

2) on the trunk interface "sh int x/x switchport"

3) configure the following (It must be enabled globally before the per-port settings take effect):

vlan dot1q tag native

4) on the previous same trunk interface "sh int x/x switchport"

Thanks to all

Roberto Taccon

Giuseppe Larosa · ‎02-24-2009

Hello Roberto,

I performed a test

Generally in the sh int type x/y switchport

only the lines with "operational" attribute describe the effective settings on the port.

For example in a new 4507 with 12.2(46)SG that we have recently installed it shows:

Administrative Native VLAN tagging: enabled

without any operational line (the port is member of a Port-channel)

if I give

vlan dot1q tag native

the show doesn't change and appears only line with administrative attribute

sh run | inc tag

vlan dot1q tag native

sh int g6/1 switchport

Name: Gi6/1

Switchport: Enabled

Administrative Mode: trunk

Operational Mode: trunk (member of bundle Po1)

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

This can be a problem in the sh output.

To check this a frame capture on a trunk port is needed

Hope to help

Giuseppe

adamclarkuk_2 · ‎02-24-2009

Hi

As has already been said, it's the operational status that matters and by default cisco does not tag the native vlan but cisco switches seem to show the Admin status as enabled.

Some switches like the ME3400 dont show you the Operational status, just the admin status so you can use the following command for quick reference

sh vlan dot1q tag native

ROBERTO TACCON · ‎02-24-2009

Hi to All,

can someone @ Cisco (maybe the TAC team)write the FINAL words about the:

- "Tagging NATIVE VLAN" is the dafault or not on Cisco switches ?

- How to check (surely) if on a trunk the NATIVE VLAN is tagged ?

Regards.

Roberto Taccon

Giuseppe Larosa · ‎02-24-2009

Hello Roberto,

I've followed Adam's suggestions

on the same c4507

sh vlan dot1q tag native

dot1q native vlan tagging is disabled globally

Per Port Native Vlan Tagging State

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

Port Operational Native VLAN

Mode Tagging State

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

Gi6/1 trunk disabled

Gi6/2 trunk disabled

Gi7/47 trunk disabled

Gi7/48 trunk disabled

Po1 trunk disabled

Po2 trunk disabled

then I add the global command

vlan dot1q tag native

I check again and I see:

sh vlan dot1q tag native

dot1q native vlan tagging is enabled globally

Per Port Native Vlan Tagging State

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

Port Operational Native VLAN

Mode Tagging State

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

Gi6/1 trunk enabled

Gi6/2 trunk enabled

Gi7/47 trunk enabled

Gi7/48 trunk enabled

Po1 trunk enabled

Po2 trunk enabled

So it is a problem of output format in sh switchport: the default is still native vlan untagged

Hope to help

Giuseppe

Florin Barhala · ‎02-19-2013

Very useful post, I had some doubts about this command, too.