I remember that Apple's AirPort base stations used to have a DHCP "Welcome Message" feature, that would display a custom pop-up dialog when computers connected to the network. How was this accomplished?

I'm trying to duplicate this feature on a Mikrotik router (for a guest network), which means I need to know the DHCP option code that was used for this. Unfortunately, I can't find any documentation on this.

I'm sure it's some kind of standard, since it works on both Mac+Windows without any extra software, but I can't find any references to it outside of Apple's old support pages -- which don't go into technical detail about how it actually worked.

Also, Apple's newer AirPort base stations don't have this feature anymore, otherwise I could just grab a packet capture. :)

(The closest I could find was Option 56 [DHCP Message], but that seems to be something else entirely.)

  • Research the term Captive Portal.
    – joeqwerty
    Commented Jun 20, 2015 at 22:38
  • Some router does not use that dhcp option. It detect you want to go on the wan, and forward the request to the welcome page.
    – yagmoth555
    Commented Jun 20, 2015 at 22:56
  • 1
    @joeqwerty: This wasn't a captive portal. It was an OS-generated modal dialog that appeared before even opening up a web browser. (And I'm not talking about automatic captive portal mini-browser dialogs that some OSes display now, either; this predated all of that.) Commented Jun 21, 2015 at 23:51

1 Answer 1


I am going to guess zero conf protocol and some local Mac service that will do the graphical part on the host.

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