FreeBSD Router Trouble

[Christopher Chan]

Honorable FreeBSD Gurus,

Can you provide much needed assistance? I have successfully setup a
FreeBSD Router, but unfortunately it's connectivity is quite buggy.

As per the traditional setup of a router, there are two ethernet
cards: rl0 and de0.
While the LAN is connected to the de0, the WAN is connected to rl0.

After 1MB or so worth of data transfer though the connection slows
down dramatically. Members of the LAN upon pinging the FreeBSD gateway
gets times as slow as 7 seconds per a packet.
When ifconfig de0 down and up, the connection is restored back to normal.

Can anyone provide me with a solution to this problem?

Thank you,

Luke