Two 255s are listed in the first two octets. This is crucial because if you misinterpret it (as in the 10.0.1.x and 10.0.2.x) and try to statically assign devices to the top of the range, you will actually be putting them into a different subnet.ДЄ simply way to find the subnet ranges (as I learned from Wendell Odom) is to take the subnet mask (say 255.255.240.0) and find the octet that is not 0 or 255 (240 in the third octet in this case).ДЇor each octet that is 255, copy the matching network number from a network address. Why this is important is because if you have a network that is an odd (say, 10.0.1.x/24) and you try to make it a /23, you will not be merging the odd with the next even (as in 10.0.1.x and 10.0.2.x) but instead you will be merging that odd into the previous even (in other words, 10.0.1.x into 10.0.0.x). I just want to add that if you go with a /23 network that your paired numbers for the subnet are even-odd. You will have to manually change the mask on statically configured devices, like your server and router, but once that's been completed then you'll be good to go. Since they are DHCP clients you can just change that setting in the DHCP server and they'll auto-adjust as they renew their leases. The fix for you is to make sure your 10.0.0.0/24 clients are actually using a /23 (255.255.254.0) subnet mask. If it doesn't match, then it will send the packet to the gateway for further routing. If the network portion (where the mask is a '1') matches, then it will send the packet directly to the destination. Essentially the sending device matches it's IP and the destination IP against the subnet mask. This means that when a device with a 10.0.0.0/24 IP (see how that works?) tries to send a packet to a 10.0.1.0/24 IP, it thinks that it must use the gateway for the packet to be routed over to the other network. To answer your question: It sounds like your subnet mask right now is set to /24 (255.255.255.0). Likewise, the all-ones host address (10.0.1.255) is used as the 'broadcast address' and cannot be assigned to a host. There are two special case numbers that we can't use there: The all-zeros host address (10.0.0.0) is called the 'network address' and cannot be assigned to a host.

255 255 255 255 ip