How do I point a client to a unicast DHCP server?

Selahattin CILEK selahattin_cilek at
Thu Nov 11 11:50:00 CET 2021

I am using FreeRADIUS 3.0.23 to deliver services on pfSense 2.5.2 ( 
FreeBSD 12.2).

Because of some rogue users, I have to issue each device a static IP 
address. I know I can do this thanks to the *dhcp_sqlippool* mod, but 
reading the *dhcp* site provided by the default install, I ran into this 

FreeBSD does *not* support binding sockets to interfaces. ...

I know a solution is suggested in the same paragraph, but I will do that 
only as a last resort.

I went ahead and added *dhcp* to *sites-enabled* anyway and then ran 
FreeRADIUS in debug mode (radiusd -X). It was a success:


listen {
         type = "dhcp"
         ipaddr =
         port = 67
*No "interface" setting is defined.  Only unicast DHCP will work*
Listening on auth address port 18127 bound to server 
Listening on auth address port 18128 bound to server 
Listening on auth address * port 1812 bound to server default
Listening on acct address * port 1813 bound to server default
Listening on dhcp address port 67 bound to server dhcp
Ready to process requests

So I see I can still use the DHCP functionality, but with a caveat: I 
must somehow get the client to ask for an IP address directly from the 
router's LAN IP address.

So my question is: Can I somehow get the clients to use unicast DHCP? In 
other words, is there some sort of RADIUS attribute I can inject into 
the authentication reply so that it will know where to get its IP from?

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