sundance-communications.com/forum Forums VOIP Phones & IP PBX Networking IP phones DHCP issues

we are running 2 w2k DHCP servers with all the scopes split over the 2 servers for resilience. we are also using layer 3 switches to seperate out the vlans into seperate subnets with a dhcp helper running on the switches to allow all sites to get their addresses from the same 2 servers. The problem is with the dhcp offers from the servers. These are the steps I would expect
data vlan = 89.0.0.0
voice vlan = 10.0.0.0
phone - dhcp discovery
server - dhcp offer (89.0.0.0 server1)
server - dhcp offer (89.0.0.0 server2)
phone - dhcp request(89.0.0.0 server1)
server - DHCP ACK
phone - DHCP release (phone will then switch to voice vlan and restart process)
what is happening is this
phone - dhcp discovery
server - dhcp offer (10.0.0.0 server1)
server - dhcp offer (89.0.0.0 server2)
phone - dhcp request(10.0.0.0 server2)
server - DHCP NACK

this is happening on both vlans and both servers. depending on which offer the phone picks up decides whether the phone will boot

any help would be greatly appreciated been working on this for a fortnight

You'll have to be more clear as to where the problem is.

If you're saying that your IP phone isn't accepting either DHCP offer... then what is the error being delivered?

What type of phone?

Give me more info and I'll be glad to help.

Sorry if that wasn't clear the problem is quite complicated. The phones are a mixture of mitel 5201,5215 and 5220's.and the problem is they are hanging on boot up this is because they are receiving the wrong dhcp address from 1 of the dhcp servers. 1 server issues an address from the correct scope and the other issues an address from the scope the phone booted on previously.Server1 and Server2 will both give a DHCP offer on the data vlan and the phone will accept 1 offer. the phone will then release the offer and move onto the voice vlan because of options in the DHCP scopes. When the phone requests an address on the voice vlan 1 the server that had given the phone it's data ip address previously will offer the correct address for the voice vlan but the other server will offer the same address it offered on the data vlan which is a diffrent subnet address this then causes the phone to fail if it requests the wrong address.
Hope thats a little bit clearer

Thanks
James

So that I understand clearly:

You have two DHCP servers. They are issuing IP addresses for two different virtual LAN segments, presumably with some type of QOS scenario.

I'm also assuming that the decision of whether or not the device falls into the data VLAN or voice VLAN is based off of its MAC address (the phone itself).

That being said. I don't see how this could be a problem. It's fairly black and white. You build a MAC address table (I don't understand why you have two different DHCP servers) that does an accept,deny order -- accept being based off of MAC, deny being all other devices fall into the data VLAN segment.

How are you controlling IP issues?

Why are you using two different DHCP servers?

What type of IP phone switch are you using, and why not allow it to use its own DHCP server, which could configure a range of addresses that would ONLY fall into a seperate VLAN segment?

Sorry for all of the questions, I just want to give the appropriate response if I can.

I just re-read your original post. So your purpose of using the two DHCP servers is for redundancy?

If that is the case, then why is the other box active? I would place it on ready alert to take over of the other box fails, and otherwise to loadbalance it for all requests. Usually it's not very common to have two active DHCP servers, as ip issue conflicts become rampant. It is however, ok to have them on seperate segments of the network. I might build it up so that they both have the IP phone mac address tables, but only one of them is active for issuing voice, and the other will automatically not issue an address for those MACs, but WILL issue an address for all other devices.

Maybe that will help.

You have to be sure your scope options are correct.
128 ip address of the 3300 controller
129 ip address of teh Controller RTC
130 string value "MITEL IP PHONE"
132 VLAN ID
133 VLAN PRIORITY (should be 6)

if any of these options aren't correct the phone will keep rejecting the DHCP offer.

Hope that helps.
Ralph