Multiple DHCP scopes in single LAN

[Layzie Bone]

The main problem I have is that the DHCP server is running out of addresses.

Our network is 192.168.0.0/24 and at the moment uses a DHCP range of 192.168.0.20-189

Not sure why the partial range and yes increasing the scope to include addresses through 254 would give me more addresses but that still may not be enough under certain conditions.

Normally I would have just changed the subnet to 255.255.254.0 which would have given me the block of 192.168.0.1-192.168.1.254 but we have a VPN through our firewall from another network that uses (you guessed it) 192.168.1.0/24

So changing the subnet is out of the question. Changing the IP addresses of all the devices to work around the issue would be impractical.

My thinking would be to create an additional scope 192.168.2.0/24 to serve guests and use DHCP reservations for our in-house devices on the 192.168.0.0/24 scope.

My question is would this work in practice? Any thoughts and advice would be appreciated.

 

[I am confused2]

So..you have your DHCP set to pass out 68 IP address's IN A HOME SETUP? Just how many IP address do you need?

Change your 0.0/24 DHCP to start at 0.2 and end at 0.254, that will then give you a total of 253 address's.

In a HOME network that is WAY more then you need UNLESS you are suppling the whole neighborhood.

 

[Apokalipse]

Or you could just pick a larger subnet range that doesn't use 192.168.1.0/24
The private ranges include 10.0.0.0/8, 172.16.0.0/20 and 192.168.0.0/16, so you can make any subnet from within those ranges.
My home network uses 10.0.0.0/16 for example.

If you wanted two DHCP scopes, because you cannot have devices connecting outside their own subnet unless there is a router in that subnet they can go through, you would either have to have:

• A router with two LAN interfaces which can be assigned their own individual IP addresses (plus the WAN interface).

• Two routers, one behind the main router. Though you could, and probably should disable NAT on the inside router (on some routers, you'd do this by changing it from gateway mode to router mode).
Assuming you had the subnets 192.168.0.0/24 and 192.168.2.0/24, your main router's LAN address is 192.168.0.1, and your second router's IP addresses are 192.168.0.2 and 192.168.2.1, you would then add the following static routes:
â—‹ On the inside router, use 0.0.0.0/0 via 192.168.0.1- this means send all traffic addressed to any other subnet through the main router
â—‹ On the main router, use 192.168.2.0/24 via 192.168.0.2 - this means send all traffic addressed to the 192.168.2.0 subnet through the second router, as opposed to through the WAN interface which it would normally do
This would look like the attached diagram.

And if you want the 192.168.1.0/24 network oven the VPN to access the 192.168.2.0 subnet, you would also have to find out which IP address their router first sees (depending on if the VPN uses a separate subnet altogether for the tunnel itself), and it would have to have its own static route for 192.168.2.0/24 via (your router)

Or alternatively, you could enable a routing protocol such as RIP or OSPF on all the routers (including the one over the VPN) and they would learn the routes from each other automatically.