Connecting another vm to your tripleo-quickstart deployment

Let’s say that you have set up an environment using
tripleo-quickstart and you would like to add another virtual
machine to the mix that has both “external” connectivity (“external”
in quotes because I am using it in the same way as the quickstart does
w/r/t the undercloud) and connectivity to the overcloud nodes. How
would you go about setting that up?

For a concrete example, let’s presume you have deployed an environment
using the default tripleo-quickstart configuration, which looks like
this:

Allocating an address using DHCP

In the above instructions we’ve manually assigned an ip address on the
ctlplane network. This works fine for testing, but it could
ultimately prove problematic if neutron were to allocate the same
address to another overcloud host. We can use neutron to configure a
static dhcp lease for our new host.