3 units conected to 1 switch and have the same subnet mask & defualt gateway:what is mostly likely the problm?

Yes they are all on the same private subnet and yes you should be able to network them together-except for Computer 3 which is in a different subnet, unless that was a typo and you meant 192.168.12.97 instead of 192.168.112 .97

Sorry about that - the previous answer has a lot more wrong than right I normally don't answer homework questions, but I do not like to see people answer with obviously wrong answers What can you deduce from the information given The 3 computers share the same gateway (192.168.12.1), so they all access the same higher level network using the same shared IP address The 3 computers are on the same subnet (192.168.12.XXX) - Because of the subnet mask, and if permissions are set correctly, then the 3 machines can "see" each other and share files on the network. If something is wrong, then the problem is most likely in the individual machine Good Luck Edit - missed the .112 - is that a typo or is that the error

Try assigning them all with the same IP. If you have a basic hub try using that first. A switch is just a slightly quicker version of a hub that roots to each port. A hub roots to all ports.

Well it's prolly a typo but computer 3's ip is not on the 255.255.255.0 subnet. Yes besides that, they should be able to talk to each other. Try pinging each one. Go to one computer and open a command prompt "start>run>type cmd > press enter. Inside the cmd prompt type ping 192.168.12.x and see if you receive replies. If you don't, it's probably a firewall issue. Make a firewall exception for icmp and file and printer sharing. If you still can't see or ping anything on the network, I am not sure so make sure to google a little about which precise services you will need for network stuff, but you will need clipbook and messenger for sure and if you want to run apps from another computer you will need the network dde services too. You can get to services by clicking start then right click "my computer" go to manage then go to services and applications then services. As far as it looks now though your IP configuration is good. My best guess is the firewall. Start>run> type firewall.cpl >select the 'exceptions' tab>click 'add port'> on the 'add a port' page click 'change scope' > either select 'my network subnet only or custom. For custom you could either put in 192.168.12.0/255.255.255.0 or you could put the specific computers and subnet like 192.168.12.2,192.168.12.3,192.168.12.4/2… I am not positive if you can put a range like 192.168.12.1-192.168.12.255/255.255.255.… but I 'think' you can. Good luck, I hope that helps.