DHCP Problem - Phones not picking up an IP from 3300

[mitelmitel]

This is the scenario on a customers site.

[Customer has a 2nd site but not sure if any config has been changed]

DHCP is enabled on the 3300.

Phone boots up it picks up option 125 but it gets given an IP from the data VLAN [off the windows DHCP scope]. Then just sits there with the IP displayed on the phones display.

The 125 Option on the DHCP server looks correct and is pointed to the Mitel 3300.

The HP Procurve switch ports are untagged for data and tagged for voice.
There seems to be an IP helper that points it to the router of the voice subnet.

When the data VLAN is disabled on a port [so that only voice is enabled] then the phone will boot up and get an IP from the 3300 no problem.

What could be the problem?

Thanks

Mitty

 

[mitelmitel]

I forgot to say - when the phone boots up it firstly dispays VLAN 20 Pri 6 before getting option 125. That seems like its picking that up from the HP switch?

 

[cknipe]

It sounds like the vlan option is missing in option 125. When the phone see's the option, if there is a vlan ID in option 125 that is different from the vlan dhcp was recieved on, the phone will release the data ip and rebroadcast for dhcp on the newly learned vlan

 

[mitelmitel]

So you think that the VLAN 20 is missing from the Mitel 3300 DHCP server 125 Option?

 

[boycey9]

I would investigate the DHCP helper a bit more, You have a DHCP server in both VLANS so the Windows one serves the Data VLAN and the Mitel serves the voice, By putting in a helper you are effectively putting two DHCP servers in the same VLAN.
The Helper Address should not be necessary in this setup.

 

[mitelmitel]

So how would I get the phones to boot up and get a an ip from the voice vlan?

 

[boycey9]

The phones will boot in to the Data VLAN get an IP address and options that tell them to reboot in the voice VLAN, they then broadcast for an Address in the Voice VLAN and boot up.

 

[mitelmitel]

So maybe all that is working but there is a problem routing inbeteeen vlans, so that when it gets it's 125 option which points to the 3300 off the data dhcp server and then tries to register to it, the routing gets it stuck on it's data ip address.

I thought you could tag the phone off the switch port so that it knows it's a Mitel phone - it boots directly on the voice vlan without going on the data vlan? Hence the helper on the HP Procurve switch.

 

[RossBC]

a couple of things that I am aware that could cause this, as it has happened to me.

a procurve will have dhcp-relay enabled by default.
from a CLI window (serial connection or telnet) type "show dhcp-relay" to verify. to disable type "no dhcp-relay". don't forget to type "write memory" to save it

secondly, a win2k3 or newer data DHCP server can be vlan aware depending on the NIC. your phone could be broadcasting for an address on the voice vlan, but the data DHCP server could be responding again. the simplest way to fix it is to make sure the port the data dhcp server is plugged into is set for untagged data and no access to voice.

thirdly, if you have a procurve, it takes less than 20 seconds to enable LLDP and as long as you don't have any non LLDP aware phones (mostly older sets and IP console keypad) then you don't even need settings in the data dhcp server. from the same CLI window, type "show vlan". if you see a column labeled "voice" then you have a procurve that has new enough firmware to support LLDP. then type "vlan 20 voice". again don't forget the "write memory"
you have just enabled LLDP and when the phone identifies itself to the procurve as a voice device, the procurve will tell it to be on vlan 20. this saves a fair bit of boot up time (especially if all phones boot at once) and eliminates any setting requirements in the data dhcp server. you still must make sure that dhcp-relay is disabled and that your data dhcp server does not have access to the voice vlan.

 

[mitelmitel]

Ross - That was a great post. This will be a good help for some testing!