Polycom IP Phones pull DHCP from wrong VLAN

Posted on 2008-11-17
Last Modified: 2012-05-05
I have a Cisco 3560 Switch that has each port configured for a data VLAN (VLAN 10) and a voice VLAN (VLAN 2).  DHCP on the Data VLAN comes from a Windows 2003 server.  DHCP for the Voice VLAN comes from a Cisco PIX firewall.

Data subnet 172.17.100.x
Voice subnet 192.168.0.x

Here is a sample config from one of the ports on my Cisco 3560 switch
interface FastEthernet0/5
 switchport access vlan 10
 switchport trunk encapsulation dot1q
 switchport mode access
 switchport voice vlan 2
 mls qos trust cos
 spanning-tree portfast

The problem is that phones when booted up pull DHCP from the data vlan.  to get them to pull from the Voice VLAN i have to hard code the switchport access to VLAN 2  on the port they are connected to.  Once they bootup and pull the correct IP, I change the switchport access back to VLAN 10.  The desktop pcs are connected to the same data cable through the phone.  If I turn the Windows DHCP server off, the phones boot up and pull the correct VLAN 2 IP address just fine.

Am I missing something in my Windows DHCP scope options?
Question by:Akostech
    1 Comment
    LVL 4

    Accepted Solution

    On a 3560 you shouldnt need to explicitly set the trunk.

    interface FastEthernet0/5
     switchport access vlan 10
     switchport mode access
     switchport voice vlan 2
     mls qos trust cos
     spanning-tree portfast

    Is CDP enabled on the Polycom?

    To double check CDP,
    6) Click on Menus > Settings > Advanced
    7) Enter admin password (default = 456)
    8) Admin settings > Network Configuration
    9) Ethernet Menu > CDP = enabled


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