[ale] Strange Linux networking issue

[Derek Atkins]

HI.

I'm having a strange networking issue between two AWOW devices running
Linux that stopped talking to each other.  The devices are configured as
below:

--(a)[Box 1](b) ----- (c)[Box 2](d)--

Where:
(a) is 172.16.5.0/16
(b) is 172.16.5.1/16
(c) is 172.16.7.100/16
(d) is 172.16.7.0/16

The (b)/(c) link is a direct link between the devices, not a crossover
cable, and no switch.

The two devices were talking fine for a while and then all of a sudden
they stopped.  Now that won't talk at all.  When truing to ping .7.100
from Box 1, it sends out ARPs but there is no ARP response from Box 2. 
Similarly, on Box 2 trying to ping .5.1 results in no ARP responses.

Both devices show the (b)/(c) link as up.  Running ethtool shows the link
is detected.  However arp -an shows an incomplete response (no surprise).

The dmesg output doesn't show anything.

I am at a loss. I don't understand how or why the two devices would stop
talking, and why neither will pick it up again.

Any suggestions for where to look or how else to debug this?

Thanks,

-derek

-- 
       Derek Atkins                 617-623-3745
       derek at ihtfp.com             www.ihtfp.com
       Computer and Internet Security Consultant