Avaya IP Phone picks up an IP from a different VLAN

[vin06357]

Hi,

I am puzzled to all this. We have Avaya IP Phones and I just installed (1) ProCurve 5406ZL switches and (1) 5308 switch. This is what I did on VLANs between the 2 switches.

The trunking port between the 5406 and 5308 are set to VLAN1 - tagged VLAN 22 - tagged. The VLAN1 is for data and VLAN22 is for voice. One of the port on 5406 where the phone is plugged into is set to : VLAN1 - untagged VLAN22 - tagged. The voice DHCP server is plugged into one of the port on the 5308 and is set to: VLAN1 - NO VLAN22 - untagged We also have a data DHCP Server(for PCs) and it's port set to: VLAN1 - untagged VLAN22 - tagged. Now here is what happened. When I turned off data DHCP server, the phone picks up an IP from the voice DHCP server. How can the phone pick up IP from the voice DHCP server? I was told that when the phone is plugged in, it gets broadcast on the default VLAN which is VLAN1. It looks like to me it gets broadcast to both VLAN(1 and 22). Am I correct? What I want is to force the phone to go to VLAN22 so it gets picked up by the voice DHCP server, not the data DHCP server. Right now the data DHCP server has a scope of 176 with info such as VLAN22, etc..so that way the phone that picks up the IP from the data DHCP server will ACK and release the data DHCP server IP and gets the voice DHCP server IP. The data DHCP server gives out 155.x.x.x The voice DHCP server gives out 172.x.x.x Let me know if you need more info than that.

Thank you,
Vincent

 

[carpetflyer]

Hmm i am not a switch expert but I think you have to add ip helper addresses which are generally used for dhcp relay agents. I have a procurve 2824 and this is what i did:

If my data vlan DHCP was 192.168.0.240 and voice is 192.168.1.1 I do:

> config
(config)> vlan 1
(vlan-1)> ip helper-address 192.168.0.240
(vlan-1)> write mem

>config
(config)> vlan 22
(vlan-22)> ip helper-address 192.168.1.1
(vlan-22)> write mem


And also do a

(config)> no dhcp-relay

to make sure the dhcp-relay is not on.

 

[vin06357]

Carpetflyer,

What will happens if I took out ip helper-address out from both vlans as well as disable dhcp-relay ? Suggestion?

Thanks

 

[carpetflyer]

The purpose of DHCP-relay is to have a DHCP on a subnet to manage the IPs for other subnets. So if you had your DHCP server (192.168.0.240) on the 192.168.1.x subnet it would assign IP addresses in the 192.168.1.x subnet.

But what if you had another subnet, say 192.168.2.x? Would you buy a DHCP server for that subnet as well? It would be a waste so DHCP-relay was invented. You allow your DHCP server to manage the 192.168.2.x subnet. Then with IP Helper addresses you tell your switch the DHCP server is 192.168.0.240. Then there are other switch commands (dont remember) that will forward all DHCP request packets to your DHCP server.

In your case you do not need DHCP-relay enabled since you have 2 DHCP servers. However, you need to create the helper addresses on each VLAN so your switch knows where to forward the DHCP request packets.

Again I am not sure if this will work on your switch since i have the 28xx series. There should be some documentation on it on the HP website. Let me know how it goes!