Duplicate ICMP messages

[Nigel Houghton]

I have a FreeBSD 4.9 box with three network interfaces setup as follows:

fxp0 - 172.16.20.2
fxp1 - 192.168.1.2
bge0 - promiscuous mode, no-arp

fxp0 is connected to a netgear switch, fxp1 is connected to a Cisco 2900xl and bge0 is also
connected to the Cisco but is listening on a span port to everything transmitted on the
192.168.1.0/24 subnet.

Here's the weirdness, when sending an ICMP Echo request to fxp1 from the switch at
192.168.1.254 duplicate replies are seen coming back. The same thing happens when sending the
same requests from fxp1 to any other address on the subnet. When the bge0 interface is brought
down the issue goes away and everything is normal.

systat shows the requests going out and the same number of replies coming back in. ipfw is
being used to deny all icmp via bge0.

I have Googled extensively for this issue to no avail, so, anyone have any ideas?

--------------
Nigel Houghton

"I have read of a place where humans do battle in a ring of Jell-O."