Recently ran into an issue where a company wanted to use multiple types of VoIP phones that required seperate settings to download their configuration with a vendor – this is usually done in a homogeneous environment via DHCP option 66 settings. (Option 66 is part of IETF RFC 2132 which states that this option uses FQDN or IP address to point to a TFTP server.) In this particular setup only one VoIP phone vendor at a time could be specified in the option 66, so custom settings were going to be needed to make all the other vendors phones work properly. Found that this could be done via DHCP reservation on either their Windows Server 2012 R2 Standard or on their Cisco 871w router, but I am sure their are ways to do it on other vendors equipment (which is outside the scope of this article). So here is how to configure the

Windows Server DHCP Option 66 Reservation

1. Turn the phone on its back and record the MAC address of the device.
2. Start the DHCP administrative tool on the server.
3. Expand the tree into the IPv4 then into the Scope needing the reservation.
4. Right Click on Reservations and choose “New Reservation…”
   
5. Give the new reservation a name, specify IP address and MAC address previously recorded.
   
6. Right click on the new reservation and choose Configure Options.
7. In the Reservation options scroll down to 066 Boot Server Host Name and enter the URL or IP of the vendors configuration server.
   
8. Make sure the vendor has reset the authorization token and factory reset the phone to pull the new reservation and configuration files.

Cisco 800 Series DHCP Option 66 Reservation Setup

Something to remember is that each reservation is treated as its own DHCP pool by the router. (I recommend exporting the configuration file to a local workstation and manually editting if there are more than a couple edits to make.)

1. Login to router and enter configuration terminal mode:
   

   Router#configure terminal

2. Enter the name of the DHCP pool as follows:
   

   Router(config)#ip dhcp pool Pool_Name

3. Enter the IP address of the device:
   

   Router(dhcp-config)#host 192.168.1.100 255.255.255.0

4. Enter the MAC address of the device:
   

   Router(dhcp-config)# hardware-address AABB.CCDD.EEFF

5. Enter Option 66 information:
   

   Router(dhcp-config)#option 66 ascii http://vendor.url/configuration.xml

6. Enter Default Gateway:
   

   Router(dhcp-config)#default-router 192.168.1.1

7. Enter DNS servers:
   

   Router(dhcp-config)#dns-server 8.8.8.8 8.8.4.4

8. Make sure to copy the running configuration to startup configuration:
   

   Router(dhcp-config)#end
   Router#copy running-config startup-config

9. Clear the current DHCP bindings to make sure the phone will grab the correct address:
   

   Router#clear ip dhcp binding *

10. Make sure the vendor has reset the authorization token and factory reset the phone to pull the new reservation and configuration files.

That is all there is to it. Enjoy a multi-vendor VoIP environment. If you need help configuring your Windows Server or Cisco IOS based router please contact us for support.