General setup
-------------
The idea is to run a virtual machine for the server, and one for the
client. We also have to run a relay for DHCPv4, because of limitations
explained in the documentation.

I used a Fedora Core 15 as the base, just because it happens to be my
desktop. I installed "virt-manager" using Fedora's package manager,
yum. (I had to reboot and turn on virtual machine hardware extensions
in the BIOS, otherwise the virtual machines would have had to been
more heavily emulated.) Then I installed CentOS 6.1 on a virtual
machine. I picked CentOS because Comcast is using Red Hat Enterprise
Linux, and CentOS is a free (as in beer) near version of that, so I
thought that would be a good test.

The install notes are here:

http://bind10.isc.org/wiki/CentOS61

In order to have a virtual network for the traffic, I created a
bridge on the host system:

  brctl addbr dhcpbr0
  ifconfig dhcpbr0 up

Then for the virtual machine, I added a new virtual network interface
using the GUI:

  "Add Hardware" -> "Network" -> "Specify shared device name" -> dhcpbr0

Now we have eth0 as a NAT to the real world through the host, and eth1
as a private network using the bridge.

I then cloned the virtual machine using the GUI, and modified a file
to make the new machine use eth0/eth1 as its interface names:

   /etc/udev/rules.d/70-persistent-net.rules

I also needed a relay, so I made another clone for that. On the relay
I installed ISC DHCP 4.x, which provides a DHCPv4 relay:

  yum install dhcp

I also installed tcpdump on all host machines to help debugging:

  yum install man tcpdump


DHCPv4 testing
--------------
In order to get DHCPv4 working, I had to disable the firewall on the
server:

  yum install system-config-firewall-tui
  system-config-firewall-tui -> disable firewall

Then I had to give the server an IPv4 address:

  ifconfig eth1 192.0.2.11

Finally I could run the DHCPv4 server:

  /opt/bind10/libexec/bind10-devel/b10-dhcp4

I also had to disable the firewall on the relay:

  yum install system-config-firewall-tui
  system-config-firewall-tui -> disable firewall

And enable the DHCPv4 relay:

  ifconfig eth1 192.0.2.12
  dhcrelay -d -i eth1 192.0.2.11

Finally I could run the client:

  dhclient eth1

And viola! The client was able to get the hard-coded lease from the
server.

DHCPv6 testing
--------------
Before the DHCPv6 work, I stopped the relay machine, and rebooted the
client and server.

For DHCPv6, the server does not need an address, but it does need to
have the interface up:

  ifconfig eth1 up

I could then start the server:

  /opt/bind10/libexec/bind10-devel/b10-dhcp6

Unlike DHCPv4, I also had to disable the firewall on the client:

  yum install system-config-firewall-tui
  system-config-firewall-tui -> disable firewall

Finally, I could run the client and it got a lease:

  dhclient -6 eth1