Did you try what high_jeeves said, CountSpatula?
Say your real IP is 224.186.67.115, and your network IPs are 192.168.0.1, 192.168.0.2 ...
Code:
(Linuxbox) (Winbox)
ISP---| Eth0 | | |
| Eth1 |---| Eth2 |
Eth0: 224.186.67.115
Eth1: 192.168.0.1
Eth2: 192.168.0.2
ShowEQ needs the network device on your Linuxbox which is connected to your Winbox and the IP of your Winbox (the internal network IP) -- a little weird, I know... o_O
For this example: in showeq.conf set network device to eth1 and IP to 192.168.0.2 (yes, 192.168.0.2, not 192.168.0.1)