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DHCP Option 43 - Mitel Phone System

Has anyone been able to get this to work with a Mitel Phone system? It requires One Bye Data type and I am struggling to get the data converted to that. Just was wondering if I am alone on this!

Category: Mid Range Firewalls


  • BWCBWC Cybersecurity Overlord ✭✭✭

    Hi @CBack85 what do you need to send via DHCP Option 43? I did this a few times for different devices and it worked fine.

    This is how I did it for elmeg as example. IIRC I created it as HEX and it got converted to DEC on the way, there was something weird going on.


  • CBack85CBack85 Newbie ✭

    Hi @BWC I need to get these options to the Mitel phones but I am not smart enough to get this converted to the One Bye Data the SonicWall requires. Any help you could provide would be greatly appreciated.;sw_tftp=;call_srv=;vlan=10;l2p=6;dscp=56;

  • CBack85CBack85 Newbie ✭

    So I got in Hex but no idea how to convert this.....


  • BWCBWC Cybersecurity Overlord ✭✭✭

    @CBack85 I don't know the format the Mitel Phone expecting via DHCP Option 43, but the string you mentioned (id:ipphone....) would be



  • ArkwrightArkwright All-Knowing Sage ✭✭✭✭
    edited July 2021

    I had to use a web developer tool to bypass form validation to allow me to paste in a string. Works fine, but not "supported" and it confuses anyone who comes along later and needs to edit it :-D

    I did raise a ticket with Support about what on earth this format is they're expecting it to be entered in. The response I got wasn't great, I was told you have to use a tool like this:

    , then you have to put a semicolon between each one, and then, maybe, you need to always start with 0; and <length of string>; eg 0; 73; if the entire string is 73 bytes long. I never managed to get this working in the format that Support suggested and it was easier just to persist with the workaround I had found.

    I think if Sonicwall insist on the string be formatted in a certain way, then they should provide a tool that can generate that format.

    No idea if the workaround works with Gen 7.

    I submitted an RFE but it never went anywhere.

    Also, if you use LLDP-MED or CDP on your switches to tell the handset what the voice VLAN is, then you don't need the first-stage DHCP lease configuring on the Sonicwall. Handset tags its packets with VLAN 10, second DHCP request hits DHCP server on Mitel phone system, badda boom, badda bing, working.

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