bridging and arp requests

[dninja at gmail.com (Robin Wood)]

Hi
I'm playing with an embeded device with two NICs in it, the device is
running running gargoyle (openwrt with a few extra features).

I've got one NIC plugged into a desktop and one into a laptop. On the
device itself I've bridged the two NICs together and given the bridge
an IP on the same subnet as the other two devices. ip_forwarding is
enabled and the cables are fine, I've checked them both.

If I try to ping from the laptop to the desktop some pings get through
but only when I ssh from the desktop to the device and do stuff
(anything, just typing). as soon as I stop activity through ssh the
pings stop.

Watching the traffic through wireshark on the desktop I can see the
desktop sending arp requests for the laptop and not getting any
replies, as soon as I do things through ssh I see ping requests come
through from the laptop and arp responses. As soon as I stop typing
the desktop starts arp requesting again, usually 3 in a row.

If I ssh to the device from the laptop and try to ping the desktop I
get no responses unless I again generate activity through the ssh
connection from the desktop to the device.

It seems to me that the device is not storing the arp table correctly
and only manages to hold it as long as a device is communicating with
it.

I've tried hardcoding the arp table on the desktop but that doesn't help.

I'm thinking it may be a problem with layer 3 switching and bridging
on the device but I don't know enough about how bridges should pass
traffic through to be able to go any further than that.

Can anyone suggest what is causing this and how I can sort it out so
that all 3 devices can talk to each other?

Robin