I have 2 computers in my network ones ip address is 192.168.2.31(PC-A) and the others is 192.168.2.33(PC-B). When I'm trying to ping from PC-B to PC-A it says:
Pinging 192.168.2.33 with 32 bytes of data:
Reply from 192.168.2.31: Destination host unreachable.
Reply from 192.168.2.31: Destination host unreachable.
Reply from 192.168.2.31: Destination host unreachable.
Reply from 192.168.2.31: Destination host unreachable.
Ping statistics for 192.168.2.33:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)
And when i'm trying the otherwise it tells me same message with ip address switched..They are both can connect to the Internet

arp -awill show you MAC addresses and associated IP addresses from the same subnet alongside your router IP and MAC. – mnmnc Dec 18 '12 at 12:08