File sharing between subnets using Windows?

At my university (and probably most universities), the different buildings on campus are split into different subnets. When I have my two Windows computers within the same subnet, they can share files fine using the usual Windows SMB protocol.

However, when I take one to another subnet, they cannot "connect" to share the files. I can ping the two computers fine, but I cannot share files. I've of course tried using the IP address instead of the "computer name", but to no avail. I've even tried using a mac from another subnet, and smb://ipaddress/ doesnt work either. But again, they can ping just fine.

So... is the SMB protocol typically not routed between subnets? Any other reason why this wouldn't be working? Besides pinging working fine, IIS also works fine on port 80.