I have a Cisco 4331 router that was configured with as a DHCP server for a small pool of Mitel iP Phones. The config of this router is a s follows:
ip dhcp excluded-address 172.20.2.139 172.20.2.142
!
ip dhcp pool Voice
network 172.20.2.128 255.255.255.240
default-router 172.20.2.142
domain-name xyz.com
option 43 ascii "id:ipphone.mitel.com;sw_tftp=10.104.0.2;10.103.0.2;call_srv=10.104.0.2;vlan=20;l2p=6v6s6;dscp=46v46s2"
!
!
The main LAN interface on the 4331 is setup as a dot1q trunk for VLAN’s 10 (Data) and 20 (Voice). The router makes a DHCP offer but the Mitel IP phone never accepts it, another DHCP request is then made by the IP Phone. The output of ‘show ip dhcp binding’ on the router shows the router offering the IP to be allocated e.g.
RTR01#sh ip dhcp bind
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type State Interface
Hardware address/
User name
172.20.2.133 0108.000f.ba4c.30 Nov 02 2017 09:52 PM Automatic Selecting GigabitEthernet0/0/0.20
I move the same DHCP config to a Cisco 887 creating VLAN 10 and 20 and trunking them on Fa0 to the switch and it works fine.
The internal switch is a HP 2920 that is configured to trunk VLAN 10 and 20 back to the respective routers. The keyword ‘voice’ is configured VLAN 20 on the HP.
Using Wireshark (port mirrored from the phone directly) the only difference I can see in the DHCP offer between the 2 x router types is that on the 4331 Option 61 (Client - ID) is in the DHCP Offer reply to the IP Phone (the phone MAC).
In the 887 I don’t see option 61 in the DHCP Offer reply. Should this even matter.
I should have connected the 887 to the same port on the switch as the 4331 and re-tested but the VLAN trunking is the same on the separate ports back to the respective routers.
Can anyone offer an opinion. It’s driving me mad. Better still has anyone got a Cisco 4K config they can share that provides DHCP for a Mitel setup.
Many thanks for taking time to read.
Regards
Darren
