IP address range

[Simon Hobson]

Jason Penton wrote:

>Lets say a relay agent is sitting on 10.31.3.10 and we want to issue
>172.16.0.0/16 addresses to all clients requesting an IP, how would one
>set that up. We can assume that the dhcp server is on 10.31.3.1
>
>if i put in the following:
>subnet 172.16.0.0 netmask 255.255.0.0 {
>      pool {
>         range 172.16.0.1 172.16.255.254
>      }
>}
>
>then when I get the relayd req from 3.10 then dhcp says there is no
>network configured for 3.10 (unknown network segment).
>
>So then i just create a subnet for 10.31.3.0/24, however I cant put
>the range of IPs (172.16.0.0/16) in that subnet because then dhcp does
>not startup, giving an error of "bad range - 172.16.0.0 not in
>10.31.3.0/25".
>
>It would be great if someone could shed some light on how I would
>configure such a scenario

What you describe is a "shared network" and there is a section in man 
dhcpd.conf on it.

The syntax is :

shared-network some-name {
   options ...
   subnet ... {
     ...
   }
   subnet ... {
     ...
   }

"some-name" is arbitrary text, so  you can use some descriptive name 
for it, eg "third-floor" or "main-building". You can include options 
common to all subnets in teh shared subnet - for example you might 
put an option in there for DNS servers.

in your case, you'd have :

shared-network some-net {
   subnet 172.16.0.0 netmask 255.255.0.0 {
     pool {
       range 172.16.0.1 172.16.255.254
     }
   }
   subnet 10.31.3.0 netmask 255.255.254.0 {
   }
}


Note that all addresses must still be unique - any subnet must be in 
only one shared-subnet.
-- 
Simon Hobson

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