Unifi DHCP Option 43 deets

29th April 2026

this is used to get Unifi devices to (Inform? announce themselves?) across VLANs

chrkov
14 years ago

I dont think that the option 43 being in HEX is ubiquiti’s choice, its just the way option 43 in DHCP was designed. I think I have a grip on it.

If I am understanding this correctly, you design the hex code as follows:

0104C0A89602

The 01 is always 01 for the UBNT equipment

The 04 is for a single IP.

The C0A89602 is your IP in HEX. In this case, C0 is 192, A8 is 168, 96 is 150 and 02 is 2.

You can use the Windows Calc to convert DEC to HEX very easily.

Then go to your Microsoft DHCP server:

  1. Right Click Server Options and then configure options.
  2. Click Option 43
  3. Enter your HEX code in the Binary Field.
  4. Click OK and your done.

Someone or anyone correct me if I am wrong.
4

Note: I would typically make Option 43 a Server Option, then it will be a default for every VLAN, make a option 43 for a specific vlan to overwrite.

source https://community.ui.com/questions/DHCP-Option-43/59fb8337-bfa1-4b7d-8e95-3780d10c3603?reply=8