well, 10.xx.xx.xx is a private IP, so it could be the router or a hardware firewall/packet filter. you could run a nmap -O scan to get some info about the OS which is running on it, which usually points also to the use of the box (but well, it might be noticed by the sysadmin of your company, so better stay away from doing it).
gogeta, you're right, most routers are using the class C 192.x adresses, but for a company the available adresses might be not enough then, that's why you can often find routers with class B (172.x) or class A adresses (10.x) which offer much more possible adresses.
