DHCP through a vlan

[oflanagan]

Hi Everyone,

I have a question regarding using dhcp through a vlan.

I have a network where I currently have a switchport set as access voice vlan11 and access vlan 10, I then connect a Mitel phone into the port and then connect my laptop into the pass through port on the back of the Mitel phone. The vlan 10 is routed to pick up DHCP from the router I have and now what I need is my Mitel phone to route to pick up DHCP which I have set on the Mitel PBX. I can get this working when I tell the phone what VLAN i.d to use however Ideally I would like to just be able to plug in the Mitel phone and for it to pick up what Vlan it is without having to program it in the phone.

Is there a way to program tghe switch that when it sees a Mitel device to attach vlan 11 to the data?

Kind regards,

Oliver.

[Mark Malone]

Hi

just so im sure here are both dhcp pools for 11 and 10 are on the local router yes ?

Have you set option 150 in your dhcp configuration ?

Is there a layer 3 SVI configured for this voice vlan with an ip address from the dhcp pool range and you default router in the pool configured as your SVI  gateway for the phones

Example

http://www.ciscopress.com/articles/article.asp?p=1745631&seqNum=5

[oflanagan]

One DHCP is on the router for vlan 10 for 192.168.10.0 netwrok and the other DHCP is in the DHCP server on the Mitel PBX, The mitel phones use option 125 and this option is on the DHCP server that sits in the PBX.

I need some how to try and tag the mitel phone to route to the DHCP server that sits in the VLAN 11.

PBX is 192.168.11.200 with DHCP scope 192.168.11.10 - 192.168.11.199

The router is 192.168.10.1 and has DHCP scope for VLAN 10 192.168.10.0 network.

Thank you.

[Mark Malone]

if the pbx is on the same subnet as the dhcp scope for the voice vlan there should be no reason that the phones cannot pick up there ip address as dhcp broadcasts ,. the only other thing is the ip helper address under the vlan 11  but thats for when dhcp scopes are sitting on a different subnet so should not be required here

have you ran a debug on the local switch when the phone is connected to see if you are recieveing an offer and if phone is sending a request to get an ip address

[Malcolm Booden]

For this to work, you need to ensure two things; the DHCP server has the correct options configured and that LLDP is enabled on the LAN switch globally or the specific switch port that the phone connects to.  The IP phone should also have LLDP enabled in the setup menu.

LLDP is the standards based equivalent to CDP in Cisco switches and plays a role in the phone knowing which VLAN to operate on when booting up, where the switchport voice vlan command is used in Cisco switches (or equivalent command in other vendor switches).

after the phone understands which VLAN it should be on for voice from LLDP, it will send a dhcp request and the DHCP server on the local subnet will provide an IP address with any required options for tftp servers and the PBX / signalling server

if the dhcp server is on a different subnet, then an IP helper is required on the layer 3 interface and the dhcp request will be forwarded appropriately.