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Registered wireless devices on central campus at MIT are typically issued IP Addreses in the 18.111.*.* subnet.
Troubleshooting
Firewalls
Until MIT decides to bring up an Institute-wide firewall, machines on campus are fully accessible and potentially vulnerable from the Internet. This has security implications for every section within the school. Hacking attacks should be expected and unnecessary guest accounts and services should be disabled on individual machines. Unprotected machines can experience slow performance or slow internet access if they're being attacked. Or at worse, the machine could be compromised if it hasn't had its updates in a while. Though Macs are rarely compromised directly in this way, Windows machines can be, especially unpatched versions of Windows XP and lower. Machines access the internet and each other through ports and firewalls should be enabled to close down any ports users don't really use.
Broken services
Sometimes there are things that you DO want a computer to do through the protection of a computer firewall, for example file sharing, screen sharing or remote management. On Unix machines like Mac OS X, these services are controlled within System Preferences. But if all your other services are running, like web access and email, but for some reason the file sharing, screen sharing, or remote management doesn't work, the best thing to do is to uncheck these network services to turn them off. Then shut down the machine. After you count to ten, turn the machine back on and turn those services on again. This should hopefully restore those services back into a working state.