To view the active connections in FreeBSD, which might be a very good debugging/overview tool for a router, one can use ipfstat -t.
This will output something like this:
Source IP Destination IP ST PR #pkts #bytes ttl
10.1.1.100,1052 199.47.216.148,80 4/4 tcp 37860 6446150 119:59:07
10.1.1.100,17500 255.255.255.255,17500 0/0 udp 11681 1740469 1:55
10.1.1.100,17500 10.1.1.255,17500 0/0 udp 11681 1740469 1:55