Hi. I have a dhcp3 server serving three different subnets (10.0.0.*, 10.0.1.* and 10.0.100.*). I have DHCP only working on one subnet as it should be. The other two only have static clients. Everyone gets their IP's correctly. I just need the different subnets to be able to speak. I have the dhcp server's subnet (10.0.0.*) set with a netmask of 255.224.0.0 which allows the 10.0.0.* and 10.0.1.* subnets to talk just fine. The 10.0.100.* subnet will not speak, however. I thought I had the netmask set correctly for this but maybe not. I am not a network Guru quite yet so could some of you veterans please help an aspiring admin?

I would try 255.0.0.0 mask but not sure wheater it should work with your settings already. Maybe You have sth wrong with DHCP settings related to 10.0.100.0 subnet.

Thanks, but that didn't work. I will have to look through some of my other settings to see what's up. It doesn't make sense to me that the only client on that subnet can get its address but can't talk to other subnets.

Ok. Its not a subnet problem. If I manually assign the IP addresses, and routes, everyone plays nice. For some reason,the machines on that subnet are not picking up their gateway even though I have the line
in the subnet container and this line works for the other subnets. I am at a loss at the moment.

If they're TRULY subnets, your need a subnet mask of 255.255.255.0. The first 3 octets define the network, the last one defines the host on the network. You need a router to route between the subnets.

If you're just creating an ip scheme that's all really just in a single 10.x.x.x subnet, then the subnet mask would be 255.0.0.0 - the 10. defines the network and the last 3 octets define the host on the network. Then you will not need a router, just a switch (or a hub).

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255.0.0.0 or 255.255.0.0 should work.


To be exact you could get the exact subnet mask by hand or calculator.

Sorry about my slow rely. Homework comes first. This is why I am still a novice networker. I guess I just have an IP scheme setup rather than true subnets. Everything goes through the same switch. I don't think my problem is subnet related anymore. I believe it has something to do with the routers option as nothing on this subnet wants to add the gateway I push to them to the routing table like everyone else does. If I add the gateway to the routing table manually, everything works just fine. I am not sure why computers aren't doing it on their own.

Make sure everything has a 255.0.0.0 netmask. SOMETHING thinks 10.0.0.x and 10.0.100.x are on different subnets and thus needs to be routed. If everything starts with 10.0, then theoretically 255.255.0.0 will work, (as should your original even broader 255.224.0.0) - I bet something somewhere has a 255.255.255.0 netmask, that's a 'class c' subnet, very common, and the default for a lot of setups.

Check those entries above in the dhcpd.conf file:

This one belongs for the first portion of the subnet that will issue the dhcp server for the client machines: (first global parameters)
and you might have a different subnet mask for the second and the third subnetwork.

So this is the last part of the dhcpd.conf check this one too: (second global parameter)

If you want to communicate between those subnets you must have the same subnet or you must insert static routes between the networks.

Anyway check the subnets you might made a mistake somewhere.

Laz.