added some host lookup commands

network.txt

@@ -251,3 +251,39 @@ flag. The way `traceroute` works is that it sends a small packet with
 a very small TTL flag, and waits to see the ICMP Time Exceeded
 message, the sender of which is TTL hops away. Note that this is not
 reliable, as paths can vary from packet to packet.
+
+
+Finding Other Hosts
+-------------------
+
+Your simplest go-to for looking up a host's IP address given its name
+is to use the `host` command:
+
+    host gizmonic.cs.umd.edu
+
+On older systems, you would use
+
+    nslookup gizmonic.cs.umd.edu
+
+This has been deprecated on newer systems, so you should always use
+`host` when available. If you want more detail about the query and
+response, you can use `dig` instead:
+
+    dig gizmonic.cs.umd.edu
+
+All of these have a number of options available to you to control what
+kinds of queries you perform. They are also able to perform *reverse
+lookups*. That is, given an IP address, they will tell you the
+(canonical) hostname:
+
+    host 128.8.130.3
+    dig -x 128.8.130.3
+
+You can also find out who registered a domain with `whois`:
+
+    whois umd.edu
+
+You can even find out who owns the subnet an address is in:
+
+    whois 128.8.130.3
+