* * * * *

                     “I've got those cable MAC blues … ”

I finally got the firewall from Condo Conner moved to the Facility in the
Middle of Nowhere, and just as I had feared, [1] our cable connection wasn't
passing traffic to it since the network card in the firewall had a different
MAC address.

I know that it is possible to change the MAC address on a NIC (Network
Interface Card) but not having done it before I had to do some research. I
found out that under Unix, it's easily done with one command:

ifconfig interface hw ether MAC address

Spring [2] and I had to leave to meet some friends, but I gave the
information to Rob [3] for him to play around with it. The idea was to change
the MAC address on the firewall interface to match the NIC in Rob's machine,
and then change the MAC address on Rob's machine, or swap out the NIC.

Upon returning home, Rob had some success with it. He was able to set the MAC
address on the firewall to match his computer and get traffic through, but
with a 60% packet loss. Looking into the problem it turned out to be that the
cable modem was set for 100Base-T while the NIC in the firewall is a 10Base-T
interface. The fix for that was to power cycle the cable modem and allow it
to sync at 10Mbs instead of 100Mbs.

But Rob didn't want to play around with changing MAC addresses—he wanted to
get the cable modem to use the firewall's MAC address. He had attempted to
call the cable provider but the technician he got did not understand what Rob
wanted. We'll be using his box for the gateway for the time being.

[1] gopher://gopher.conman.org/0Phlog:2002/02/14.3
[2] http://www.springdew.com/
[3] http://www.tragic-smurfs.com/

Email author at [email protected]

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