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Community Member

Anyone using the Cisco 300 Series switches? Unable to get Auto Voice VLAN to work

Im playing with a SG300-10MP in a lab for a potential client purchase.


I am unable to get the Auto Voice VLAN function to work correctly.


I have set the “user ports” as untagged for VLAN 20 (data vlan)


Under VLAN Management -> Voice VLAN -> Properties, I have defined VLAN 30 as the voice vlan and enabled the auto voice vlan with activation immediate.  CDP and LLDP are all configured (defaults).  Smartport features are all defaults.


I have connected two IP Phones – a 7941 and and a 7940.  Both draw an IP address from the attached router (port 9 on the switch is configured as a trunk up to a router running DHCP) – but an IP address out of the data VLAN.  As they don’t get an Option 150 address, they don’t register.


When I look at the Smartport Interface settings for ports 7 and 8, it indicates Smartport Application Method is disabled as the Smartport Type is Unknown.


I also attached a regular laptop to Port 5 on the switch.  It drew a data vlan IP address and it too showed up as Smartport Type Unknown


So, I ran the diagnostics on the two ports to which the IP phones were attached.  The macro is failing at the line


“smartport switchport trunk allowed vlan add $voice-vlan


So, this makes sense to me.  The macro is not applying the voice vlan to the switchport, hence the phone is not getting the correct vlan and thus not getting the correct dhcp scope and tftp service IP address.


So, the question is, why is the macro failing?


I go back to the Voice Vlan properties page and confirm that I have 30 set for the voice vlan and that I have applied the change.  The page shows that the operational status of the voice vlan is 30.


Anyone run into this or have any suggestions?




Community Member

To confirm if IP Phones are

To confirm if IP Phones are working you can try:

- disable Administrative Auto Smartport

- enable Telephon OUI

- in Table OUI add first 3 octets from IP Phones mac address

- enable ports in Telephone OUI Interface menu (Trunk port connected to the router should stay disabled)

After that Port VLAN Membership should show 'Operational VLANs' 20UP and 30T for ports with phones.



Hello Jeff,I have seen this

Hello Jeff,

I have seen this before, and I also set it up in my lab just now to confirm it.

If you'll notice the macro code for IP Phone + Desktop does not include a switchport mode trunk command.  It assumes the ports will be at their defaults, and just starts trying to add VLANs.  If you have changed the port to be access this won't work, and the macro fails here.

If you have changed your ports to access go ahead and switch them back to trunk. Then this macro will execute without any issues.  I will bring it up with L2 that this should probably be changed to at least attempt to put the port in trunk mode, so that this error doesn't happen anymore.

I know that with IOS you set access ports and add an auxiliary voice VLAN, but the Small Business switches work a bit differently, we need to be in trunk mode for phones with PCs behind them (or possibly general, it seems like that would work to).

Hope that helps,

Christopher Ebert - Advanced Network Support Engineer

Cisco Small Business Support Center

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