I have a Cisco 2621 router in front of a Watchguard Firebox III 700. The interface (FastEthernet0/1) IP on the Cisco facing my LAN is 100.200.300.1, for example. The IP on the FBIII external interface is 100.200.300.2.
Using any computer behind the FBIII, if I ping the Cisco at 100.200.300.1, 50% of the packets are dropped. Likewise, from the Cisco, if I ping the FBIII at 100.200.300.2 50% of packets are dropped.
Any packets passing through the Cisco (the router is not the source or destination) seem to be fine, i.e. no packet loss.
As a result when I try to copy the system image from the Cisco to a TFTP server behind the FBIII, some data gets through but the copy eventually fails. The copy status on the Cisco console looks something like this
A period represents a timeout and a bang represents 10 packets sent.
I'm leaning toward the issue being with the Cisco router but I'm not positive. I'm wondering if anyone has seen this behavior and has any helpful hints.