Cant Change Cisco 7940 Operational VLAN Id

Posted on 2007-10-19
Last Modified: 2012-06-27
    I'm changing some network settings on a 7940 cisco phone.  I'm able to edit some things but when I try to edit the "operational vlan id" I loose the softkey "edit"  any ideas on what to do anyone?

Question by:sean-keys
    LVL 22

    Expert Comment

    There are basic user and administrative modes to the 7940. mostly likely you're locked out of admin mode which will prevent you from changing settings. What kind of setup are you running? Call Manager? Asterisk?

    Author Comment

    CM, I'm trying to test it with an Asterisk system.  I take it I have to unlock it somewhere in CM?
    LVL 22

    Expert Comment

    you might have to change the firmware on it if you want to run it on asterisk. Not sure of the latest. haven't played with them much recently. you can unlock the phone in the config file that gets pushed from CM or on the phone itself.


    go to the section on network settings. Short version:
    Step 1 Press **#

    This step either locks or unlocks the options, depending on the previous state. Continue with Step 2 to view the padlock icon.

    Step 2 Press settings.

    Step 3 Use the Navigation button to select Network Configuration.

    Step 4 Press the Select soft key.

    Step 5 Look at the upper-right portion of your LCD.

    "LockedThe icon displays a locked padlock.

    "UnlockedThe icon displays an unlocked padlock.

    LVL 3

    Accepted Solution

    You can not change the Admin ID directly from the phone. The "Admin VLAN" is specified from the switch using the "Native VLAN" command on the interface on which the phone is connected (this is assuming the switch is also Cisco. So admin vlan is the defult vlan which the IP phone passes on to the PC port. If you wish to change this you must modify the switch configuration.

    Here is an example of the VLAN configuration on the switch:
    interface Vlan100
     description ### DATA VLAN ###
     ip address
    interface Vlan200
     description ### VOICE VLAN ###
     ip address

    and how we assign the VLAN's to the switch interface and identify VOICE vlan:
    interface GigabitEthernet1/0/1
     description ### Trunk Link to Cisco IP Phone ###
     switchport trunk encapsulation dot1q
     switchport trunk native vlan 100
     switchport voice vlan 200
     switchport mode trunk

    If you connect a PC (without first connecting to a phone) to a switch port which is configured as trunk port, the switch will assign the PC to VLAN100 because this is marked as the "Native VLAN". All devices will be assigned to the Native VLAN unless the switch knows it is an IP phone connecting... as mentioned the switch knows when a Cisco phone is connected (by use of CDP protocol) and assigns the phone to the VLAN marked with "switchport voice vlan xxx"

    Hope that helps...
    LVL 3

    Expert Comment

    PS. Also my post applies to use with ALL Voip systems - because the "Admin VLAN" value is determined by the switch, not the phone or the Voip PBX.

    Author Comment

    How does CDP know that a certain device is a phone.  The only way I'm familiar with assigning devices to vlans is with a vtp server that contains mac/vlan mapings.  Also it seems I will need a separate switch that supports vlans in order to create a true test environment.
    LVL 22

    Assisted Solution

    couple of things. first off, yes your switch will need to recognize vlans and do trunking if you have data behind the phone. Cisco will do discovery on it's own products but as far as I know only cisco switches and cisco phones will do the auto discovery via CDP. This is actually the ideal if you're a cisco shop since you can also set the switches and routers to do auto qos (to a large degree). If you are using some other switches or some other phones (the Linksys SPA phones for example don't support CDP as far as I can tell) you'll have to manually set the VLAN ID on the endpoints AND setup dot1q trunking on the switchports.  

    For example one of the solutions i work with regualry uses Snom phones and Adtra switches. On these, the end devices must specify the VLAN they're going to use and the switchports must be configured for VLAN trunking with the same switchport trunk native vlan XXX command. Doing this only on the switches will not work in a non-Cisco environment as the discovery protocols are proprietary. In your case this probably doesn't matter unless your switches are not cisco.

    final small note if you setup the multiple vlans on the switch, the ip addresses on the two different vlans should be different. Different subnets for each VLAN. minro typo in the switch config above, but something to keep in mind as you do your addressing schemes.

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