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VoIP Phones not getting DHCP address from correct vlan

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Occasional Visitor

VoIP Phones not getting DHCP address from correct vlan

I am trying to add a V1910-24G switch to our existing HP Network.  My problem is that VoIP phones are not being added to the proper Vlan.


Existing Network is HP 5406ZL switches:

One DHCP Server on Vlan 1 with 2 scopes, one for Vlan 1 (PCs) and one for Vlan 35 (VoIP)

Vlan 35 has an IP Helper configured to point to the DHCP Server on Vlan 1

Ports are configurd Untagged for Vlan 1 and Tagged for Vlan 35

When a Phone is connected, it gets a Vlan 35 address.  When A PC is connected to that phone it gets a Vlan 1 address.


The V1910 switch has Vlan 35 created with an address assigned.

DHCP Relay is enabled for Vlan 35 and the address of our DHCP Server on Vlan 1 specified

I am using port 24 as my uplink (Untagged = Vlan 1, Tagged = Vlan 35, Link Type = Trunk)

The port it connects to is set (Untagged for Vlan 1, Tagged for Vlan 35)

Voice Vlan settings on the V1910 switch for all ports except 24 are (Security = Enabled, Vlan Port Mode = Enabled, Voice Vlan Port State = enabled, Vlan ID = 35)

Ports are configured Untagged for Vlan 1, and Tagged for Vlan 35, Link type = Hybrid

When I connect a Cisco phone I get a DHCP address from Vlan 1.


Any idea why?  Do I need to setup a special route for the DHCP relay between vlans? and if so, how?


Re: VoIP Phones not getting DHCP address from correct vlan

Are these older cisco phones?  If so try these commands.  Havent used a v1910, so not sure if they are available....



cdp mode pre-standard-voice
power-over-ethernet pre-std-detect ports 1-23


Also no need for ip address on vlan 35, ip addresses are for management or routing only.  Nor should you need ip-helper address as that is configured on your 5406 which I am assuming is doing the routing.


When all fails, configure the vlan on your phones and see if it works.

Honored Contributor

Re: VoIP Phones not getting DHCP address from correct vlan

I guess you should configure the 1910 to be similar to the 5406: your phone ports are configured as trunks on the 5406, so get rid of "hybrid" from the 1910s and make them trunks.

Then, you have this "Voice vlan port state=enabled" - what does that do? 


Finally, how does the Cisco phone know which is the tagged Voice VLAN on the 5406? Does the 5406 have LLDP?

Occasional Visitor

Re: VoIP Phones not getting DHCP address from correct vlan

Found the solution to this!  All the settings I had were correct, but what I was missing as enabling the CDP protocol.  Without CDP enabled the HP software couldn't determine they were VoIP devices connecting and so didn't assing the correct vlan.


Under Networking, LLDP I had to enable CDP globally and then for each port I had to set the CDP mode to TxRx.  Once that was done the switch assigned the vlans properly.