Re: [gentoo-user] Two wifi client interfaces and routing

[Grant Taylor]

On 3/31/22 10:17 AM, Grant Taylor wrote:
> I do know that the DHCP protocol supports adding additional options /
> definitions / parameters (?term?) to specify ... static routes.

In case others are interested in this, a few pointers about using it.

ISC's DHCP server has two options for advertising routes that clients 
should install;

    subnet ... netmask ... {
       ...
       option cidr-static-route ...;
       ...
       ms-static-route ...;
       ...
    }

Both *-static-route options use the same format and the format took a 
little bit to wrap my head around.  It consists of sets of <netmask 
length>, followed by the <network bits>, followed by the router.  E.g.

    option cidr-static-route 10, 100, 64, 192, 0, 2, 123, 0, 192, 0, 2, 1;

That says:

  - 100.64.0.0/10 is reachable via 192.0.2.123
  - 0/0 is reachable via 192.0.2.1

ProTip:  Go ahead and add the default gateway 0/0 route to the 
*-static-route entries as some clients ignore the option routers entry 
when *-static-route option is present.

I have multiple macOS, iOS, Windows 10, Linux, and other esoteric things 
correctly using a route to a lab / sandbox subnet via a system that 
isn't the LAN's default gateway.

Finally:  This seems to be a well defined DHCP standard, but seemingly 
not well known option by the various people that I've discussed this with.



-- 
Grant. . . .
unix || die