help, i'm setting up a router

[deeptech71 at gmail.com]

Hi,

I'm making a FreeBSD router with ppp and telnet access to it (currently part of 
a network with a hardware router). When I have 1 NIC in the FreeBSD machine 
(rl0), telnet works fine. Then I add another NIC (ed0). Telnet still works. rc.conf:

   ipconfig_rl0="inet 192.168.123.251 netmask 255.255.255.0"
   #ipconfig_ed0="inet 192.168.123.251 netmask 255.255.255.0"
   hostname="qw.erty.com"
   defaultrouter="192.168.123.254"
   inetd_enable="YES"
   gateway_enable="YES"

My PC (192.168.123.111) is hooked up with the FreeBSD box, and through that, to 
the hardware router. In both cases, when the second line is commented or 
uncommented, routing doesn't seem to work. (Even if I change the second IP 
address, but why would that be good?) However, when it's uncommented, I can't 
connect to the FreeBSD via telnet! Errors on the FreeBSD screen, when my PC is 
hooked up with rl0:
     ed0: device timeout
and when hooked up with ed0:
     kernel: arp: 192.168.123.111 is on ed0, but got reply [a MAC address] on rl0
WTF?!

I have low experience with FreeBSD. What more should I do to make the routing work?

One more question, what files does sysinstall edit (such as /etc/rc.conf) when 
configuring network interfaces?

Thx