[TriLUG] DHCP Problems and a Network Tap

[Sean Alexandre]

I'm still debugging a sporadic DHCP problem. I've got a Debian firewall
attached to my Time Warner cable modem (bridge mode). Sometimes it can complete
the DHCP handshake and get an IP address. Other times it can't.

I've got a laptop that can always get one.

I've used wireshark to look at details, and have configured the firewall to
give the same DHCPDISCOVER request as the laptop. Everything's identical,
including MAC address, but I still don't get an DHCPOFFER back.

I want to put a network tap (or hub) on the connection coming from the firewall
so I can see the actual traffic. Anybody know where I could get one? Ideally
I'd like to find one locally or build one.  (I've already checked Intrex.)

I found these instructions, and may end up trying this:
http://www.instructables.com/id/Make-a-Passive-Network-Tap/?ALLSTEPS

Anybody got a hub they want to get rid of (or router with a tap port)?

Or, any other suggetions?