DHCP VLAN Option 132

Sangoma S-Series IP phones support VLAN discovery via DHCP Option 132; other series of Sangoma phones do not. When the VLAN Discovery method is set to DHCP, the IP phone will detect DHCP option for a valid VLAN ID. The predefined option 132 is used to supply the VLAN ID by default. You can customize the DHCP option used to detect the VLAN ID.  Before using DHCP VLAN feature on IP phones, you must make sure that the DHCP option on the DHCP server is setup properly.

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• If you have not mapped your phones Mac address to a extension and template you will need to do that now.  If you have already then the config for those phones should be updated and you can skip to the steps below.

  • Go into Extension Mapping and Map your Mac Address to an extension, brand, model and template.  This will build a configuration file for your phones mac address that enables DHCP Vlan and disables LLDP.

    

  • Boot the phone and have it retrieve the updating configuration file from a non tagged vlan using our redirect server as outlined here or option 66 on your DHCP server as outlined here.
    

• Recap on what will happen

  • Phone boots up on untagged network and option 66 or redirect server is set to send the phone to the PBX for a configuration file.

  • In the template that the phone will use, you have option 132 enabled as shown above in the VLAN DHCP and disabled LLDP

  • The boot will pull its configuration on boot and receive the information to enable options 132 and disable LLDP

  • The IP phone broadcasts a DHCP Discover message to find out if there is a DHCP server available.

  • If the DHCP server sends a DHCP Offer message with the Option 132, the phone will accept the Offer, send a DHCP Request, and save the VLAN ID provided by the DHCP server in the DHCP option 132.

  • After the DHCP server has sent the ACK message to the phone, the phone will release the leased IP address and start a new DHCP Discover cycle using the now known Voice VLAN ID tag.

  • After this process, the phone will send all packets with the VLAN ID learned from the DHCP server in the DHCP option 132.

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