per-pool routers in dhcpd.conf?

[Sten Carlsen]

> On 25 Jul 2020, at 16.23, Alexis Huxley <alexishuxley at gmail.com> wrote:
> 
> Hi, I have dhcpd.conf at home containing:
> 
> 	host { ... }
> 	...
> 	
> 	subnet 192.168.1.0 netmask 255.255.255.0 {
> 	    option routers 192.168.1.1;
> 	    option domain-name "pasta.net";
> 	    option domain-name-servers 192.168.1.21;
> 	    option ntp-servers time.pasta.net;
> 	
>            #  1-100 are reserved for statically configured hosts.
> 
> 	    #  101-150 are reserved for known dynamic hosts (known because they're in host stanzas above).
>            #  e.g. my Android phone on wifi.
> 	    pool {
> 	        range 192.168.1.101 192.168.1.150;
> 	        allow known-clients;
> 	        deny unknown-clients;
> 	    }
> 	
> 	    #  151-200 are for unknown dynamic hosts. e.g. visitors' phones on wifi.
> 	    pool {
> 	        range 192.168.1.151 192.168.1.200;
> 	        allow unknown-clients;
> 	        deny known-clients;
> 	    }
> 	}
> 
> This works fine. 
> 
> I now want to force 'known dynamic hosts'' to use a different gateway. 

For what it's worth, my setup uses 2 pools in the same network where one pool has a gateway and the other pool has no gateway. These are separated by class and subclass statements. I have another pool for unknown clients, they get a different network and no gateway (can't talk to any other host and no access to internet).
This setup works fine.

> 
> (In case you're curious: Since, when using wifi, my Android
> phone silently refuses to use the DNS server proposed by the above
> dhcpd.conf, I now want to change the phone's gateway to a masqueraing
> Linux box, where I can hopefully use iptables to force the phone to
> use the DNS server proposed by the DHCP server, and thereby block ads.)
> 
> The dhcpd.conf man page says:
> 
> 	In general, any parameter can appear anywhere that parameters
> 	are allowed, and will be applied according to the scope in which
> 	the parameter appears.
> 
> and I don't see anything special documented about 'option routers'.
> 
> So I thought this should work:
> 
>        subnet 192.168.1.0 netmask 255.255.255.0 {
>            #option routers 192.168.1.1;               <--- commented out at subnet level
> 	    ... 
> 
>            pool {
>                range 192.168.1.101 192.168.1.150;
>                ...
>                option routers 192.168.1.32;           <--- this is the different gateway
>            }
> 
>            pool {
>                range 192.168.1.151 192.168.1.200;
>                ...
>                option routers 192.168.1.1;            <--- this is the original gateway
>            }
> 
> but it looks like *no* host gets told its gateway. 
> 
> To confirm that it wasn't a problem with my new gateway itself, I
> put the original gateway in *both* pools, i.e. only the *location* of
> the router declaration changes compared to the original configuration:
> 
>        subnet 192.168.1.0 netmask 255.255.255.0 {
>            #option routers 192.168.1.1;               <--- commented out at subnet level
> 	    ... 
> 
>            pool {
>                range 192.168.1.101 192.168.1.150;
>                ...
>                option routers 192.168.1.1;            <--- this is the original gateway
>            }
> 
>            pool {
>                range 192.168.1.151 192.168.1.200;
>                ...
>                option routers 192.168.1.1;            <--- this is the original gateway
>            }
> 
> The result was the same: no gateway.
> 
> My googles didn't turn up anything relevant and my experiments (using
> 'groups' failed), so any advice would be appreciated. I'm using 
> isc-dhcp-server 4.4.1 on Debian 10. Thanks!
> 
> Alexis
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