Voice Vlan command

Just curious why this happens...

We run Vlan 200 for users in our building. In anticipation of a pilot voice rollout next weekend, I added the "sw voic vl 201" command in an interface-range, and lost connectivity to every port in the range.

I understand that "mls qos trust cos" and "trust cisco-phone" commands are required before adding phones, but I didn't expect the voice vlan command, on its own, to bring down the switch.

Any thoughts?

Find more posts tagged with

Comments

pitviper

Doesn’t sound like the “typical” result that I would expect (Unless of course you were messing with a trunk, SVI, or the native vlan config

). What type of switch is it? Do you have a switchport config handy?

Something like this is pretty basic:

interface FastEthernet0/1
switchport access vlan 200
switchport mode access
switchport voice vlan 201
mls qos trust device cisco-phone
mls qos trust cos
spanning-tree portfast

(The phones will still work without the qos commands - even with them if you don't "act" on the markings later on they won't actually do anything)

mikearama

Yeah, I was surprised too.

Turns out that my partner had disabled mls qos on the stack (it's a 3750X stack, 8 switches). As soon as I reentered the "mls qos" global command, ports with the voice vlan config'd began to work. Interesting.

chmorin

mikearama wrote: »

Yeah, I was surprised too.

Turns out that my partner had disabled mls qos on the stack (it's a 3750X stack, 8 switches). As soon as I reentered the "mls qos" global command, ports with the voice vlan config'd began to work. Interesting.

Two things come to mind... lol:

1) I didn't think that interface connectivity would drop if qos was configured on a port and then disabled... didn't see that coming.
2) Why in the world would your partner disable qos during a voice implementation? XD

Glad that you solved it.

APA

hmmz that doesn't sound right...

voice vlan isn't tied to mls qos as far as I'm aware...... the fact it dropped the switch when turning on mls qos is worrying....

I haven't really played with 3750X stacks.... but I'd assume they aren't too much different from the original 3750 stacks... apart from additional features (10GE etc...)

What is the port config like where you added the voice vlan?

have you got access vlans applied to ports that have negotiated trunks via DTP?

chmorin

APA wrote: »

hmmz that doesn't sound right...

voice vlan isn't tied to mls qos as far as I'm aware...... the fact it dropped the switch when turning on mls qos is worrying....

I haven't really played with 3750X stacks.... but I'd assume they aren't too much different from the original 3750 stacks... apart from additional features (10GE etc...)

What is the port config like where you added the voice vlan?

have you got access vlans applied to ports that have negotiated trunks via DTP?

Eh I have not been able to reproduce the problem. Not sure how QoS is related to switch interface status.

mikearama

Hey, I'm with you. I don't know why she did it.

Interface set up looks like:

!
interface GigabitEtherenet1/0/1
switchport mode access
switchport access vlan 300
switchport voice vlan 210
!

and that's across the board for the entire switch.

So when we brought the stack up, I couldn't get a connection on any port in the stack. Only when I removed the voice vlan command did a port begin to work.

After not being able to locate the "mls qos" command in the show run, I added it, and now have connectivity on every port.

And nope, no ACL's anywhere on these switches (oops... except for snmp access).

Mike

chmorin

When you say couldn't get connection, what exactly do you mean? I'm curious now XD since I'm leaning QoS.

mikearama

Nothing beyond layer 1. No IP address, no ability to do anything. A link light, but nothing more.

Before I realized that qos was disabled, I removed the voice vlan from the interface I was connected to (via console), and voila... got an IP and everything was fine. Duplicated this two more times before I realized "mls qos" was missing.

I'm about to setup another new 3750X stack to replace an existing non-poe 3750 stack... I'll try it again. Let you know.

laidbackfreak

Interesting results, out of curisosity which ip range is your pc on ?

and before removing the voice vlan via console were you conected via ethernet ?