DHCP "force" function - possible?

Installing and Using OpenWrt Network and Wireless Configuration
1

Hello everyone,

We are currently using a classic Linux DHCP server. However, this is to be replaced because it is causing increasing problems and we have hardly any options for changing anything. It is also very old.

I have now installed OpenWRT on a FRITZ!Box 7530. Everything is running well. PPPoE is also online.

Now we would like to provide a DHCP server with option 43 via LAN 2-4. The routers connect to our ACS server via URL using DHCP option 43. Now the first question is whether I can specify a complete URL with port details?

And then the option should be included in the DHCP offer. This apparently works with Linux DHCP; with Mikrotik, for example, the ‘force’ function for DHCP options was distributed via an update.

Is this also possible with OpenWRT? Problem why this is necessary: The routers do not request the option. It has to be forced on the routers.

BR Tim

2

Yes you can do this with a list dhcp_option_force in the config dhcp section of /etc/config/dhcp. Option 43 is the free-form "vendor specific" option which can send any sequence of bytes that you want. The data must be converted and listed in hex. The first two bytes are the vendor subtype and the length to follow. For example here is how to advertise to Cisco APs that their controller is 10.1.1.5

list dhcp_option_force '43,f1:04:0a:01:01:05'

Also there is dhcp_option which conventionally sends the element only if requested.

3

Thank you for the quick and precise answer. Is this only possible via SSH or also via GUI?

4

I think the GUI only has a way to set dhcp_option, not dhcp_option_force.