DHCP RElay Help

Simon Hobson dhcp1 at thehobsons.co.uk
Thu Mar 13 16:37:23 UTC 2008

Rhino Lists wrote:

>Thanks for the help.  I had to put the new subnets into a new shared network
>of its own.  Now everything works as expected.  Just out of curiosity why
>would having all the subnets in one shared network try to issue wrong IP's
>to the other interface?


A shared network is a network segment where you have more than on IP 
subnet sharing the same physical wire (technically broadcast domain I 
think). Thus a device on the physical network may have an address 
from any of the subnets.

The shared-network declaration tells the dhcp server about this setup.

What you seem to be asking is, if I falsely tell the server that ALL 
my subnets are on the same bit of wire, why does it get things wrong 
? The answer is that your configuration file must accurately depict 
your network. If you have two subnets which are separated by a router 
and do not share the same wire, then they are not a shared network 
and must NOT be put into the same shared network declaration as each 
other. It IS valid to have more than one shared network, each one 
containing a number of IP subnets, but with a router between each 
shared network and any other network or shared network.

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