DHCP Broadcast Relay

[anthonymeluso]

I just need some help understand something with DHCP broadcast over routers.

Here is the situation. My DHCP server is on the 192.168.1.x network and all computers on that side of router should get an 192.168.1.x address from the DHCP scope that I had created.

Now if I create another scope for the 192.168.2.x network and enable DHCP relay on my router would both broadcast cross over to the 192.168.2.x network or would just the scope for 192.168.2.x

Could someone explain this to me better I'm a bit confused.

Thanks.

Anthony

 

[Saugilsr]

Not exactly.
The port belonging to the new subnet acts as the DHCP forwarder. (Not the whole router). So when that port recieves a DHCP request (from its attached subnet) it will forward the request onto the proper subnet (port) on which in the server is located.
The DHCP server knows which scope to respond with because it becomes part of the forwarders request. The response if given and the forwarder passes it back to the original requester.

So really DHCP broadcasts are generated and reapeated all over the place. Typicaly on a cisco router you can tell it the exact ip of the dhcp server or a given range.

Hope that makes sence.

 

[anthonymeluso]

Yeah it does.

So a computer on the 192.168.2.x subnet would request a IP address and the router would pass it to the network the DHCP server is on. It would then get an 192.168.2.x address right?


Thanks for the help,

Anthony

 

[Saugilsr]

Correct.

.. and just to correct something in my previous post that should say "are NOT repeated". So the request isn't repeated to every other possible route like a broadcast storm.

 

[anthonymeluso]

Thanks

Anthony