Tuesday, July 1, 2008

Ghetto OpenBSD Firewall\Switch

In an attempt to clear even more stuff off my desk, I created a ghetto OpenBSD firewall\switch. Basically, I added four network cards to an old Dell Precision 350. Loaded OpenBSD on it. Went the standard route when creating a firewall. The five network cards on the system are em0 (External), dc0 (Internal), dc1, sk0, sk1.

echo 'inet 169.xxx.xxx.xxx NONE' > /etc/hostname.em0
echo 'inet NONE' > /etc/hostname.dc0

Then I configured the remaining cards.

echo 'up' > /etc/hostname.dc1
echo 'up' > /etc/hostname.sk0
echo 'up' > /etc/hostname.sk1

Configured a Bridge between the Internal card and the three other cards.

echo 'add dc0 add dc1 add sk0 add sk1 up' > /etc/bridgename.bridge0

Using the same NAT rule set I had before (listed below) and with a few crossover cables (had my student assistant work on that portion) I now have a ghetto OpenBSD firewall\switch. Finally, I have a use for all those extra network cards and old systems laying around the office.



testDomain = "{}"

set skip on lo0
set loginterface $ext_if

nat on $ext_if from $testDomain to any -> $ext_addr

pass in on $int_if all
pass out on $int_if all

block in log on $ext_if all label "Default block in"
block out log on $ext_if all label "Default block out"

pass out on $ext_if proto tcp from $ext_addr to any port { http https } \
flags S/SA modulate state

pass out on $ext_if proto udp from $ext_addr to any port { domain }

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