I'm using Cisco Package Tracer Student to test some networks. But I'm getting the error "Invalid IP for this subnet mask" when I try to set the IP of a PC as 10.1.1.255 OR 10.1.2.0 and the mask as 255.255.254.0, this network is supposed to be an /23 so the valid range should be from 10.1.1.1 to 10.1.2.254.
If I set the PC's IP as 10.1.0.255/23 it works, just as 10.1.1.0/23. Why can't I use those I need?
Best Answer
It's because those are invalid host addresses for your network. You are trying to straddle the boundary between two different networks for that network mask.
The broadcast address for your network,
10.1.0.0/23
, is10.1.1.255
, which is the address you are trying to use.The network address for your network,
10.1.2.0/23
, is10.1.2.0
, which is the address you are trying to use.You could use the addresses you want to use if you use a shorter network mask, e.g.
/22
.