Update docs.

README.md

@@ -6,11 +6,12 @@ Ubuntu cloud images onto local virtual machines.
 ## Prerequisites
 
 This set of scripts was developed on Ubuntu 16.04 LTS (Xenial). It is not
-guaranteed to work on any other platform.
+guaranteed to work on any other platform. (At least one script requires
+`python3` at the time of this writing.)
 
 First, you'll need to ensure the following packages are installed:
 
-    sudo apt install libvirt-bin qemu-kvm virtinst python3-netaddr
+    sudo apt install libvirt-bin qemu-kvm virtinst
 
 Your `~/.ssh/authorized_keys` file *MUST* be populated with whatever keys
 you wish to use with the virtual machines. The cloud images do not have
@@ -47,6 +48,18 @@ After you've finished with the virutal machine, you can easily delete it
 This repository also contains a few helper scripts, which can be helpful
 (assuming, as the scripts do, that you are using `virbr0`).
 
+### `get_mac`
+
+Utility to return a consistent MAC address given the specified hostname. This
+is useful so that when tearing down and recreating virtual machines with the
+same name, consistent MAC addresses are used, which should cause `dnsmasq` to
+hand out consistent IP addresses as well.
+
+### `get_ip_via_arp`
+
+Utility to return (based on `virbr0`'s ARP cache) the IP address for the given
+hostname, assuming the hostname's MAC was generated by the `get_mac` script.
+
 ### `ussh`
 
 The `ussh` utility stands for **Untrusted SSH**. It is a wrapper that allows
@@ -55,21 +68,14 @@ SSH without checking the key of the remote system.
 ### `vssh`
 
 The `vssh` utility stands for **VM SSH**. It is a wrapper which attempts to
-look up the IP address of the virtual machine (based on `dnsmasq`'s idea of
-that host mapping), then runs `ussh` to open a session.
+look up the IP address of the virtual machine (based on the ARP cache and the
+expected hostname-based MAC from the `get_mac` script), then runs `ussh` to open a session.
 
 ### `vcleardns`
 
 Utility script to clear out `dnsmasq`'s lease database for `virbr0`.
 Also restarts the `libvirt-bin` service.
 
-### `get_mac`
-
-Utility to return a consistent MAC address given the specified hostname. This
-is useful so that when tearing down and recreating virtual machines with the
-same name, consistent MAC addresses are used, which should cause `dnsmasq` to
-hand out consistent IP addresses as well.
-
 ### `vdig`
 
 Wrapper to use `dig` to query the `dnsmasq` running on `virbr0`.