add CloudStack limitations

docs/cloudstack.md

@@ -165,3 +165,16 @@ The world's your oyster! 😊
 
 If you plan on hosting a publicly available website, you will want to create
 a virtual host. See [Virtual Hosting](../vhosts) for details.
+
+## Limitations
+There are a few limitations of our CloudStack setup which are worth knowing:
+
+* The console proxy will only work if you're on the campus network. See
+  [SSH Tricks](../ssh-tricks) for instructions on how to set up a SOCKS proxy.
+* If you're uploading a template or ISO from your computer, you also need
+  to be on the campus network.
+* If you're creating a template which downloads an OS image from a URL, and
+  that URL resolves to a machine on campus, it won't work. There's some
+  iptables setup which we (syscom) need to do beforehand; just send us an
+  email if you're going to be downloading a template from an on-campus
+  server.