[ale] Strange Linux networking issue

[Jim Kinney]

???
Two hosts directly connected with neither switch nor cross-over cable.
???

Sounds like the two nics auto-negotiated themselves to death.

To test, stop networking on boxA, rmmod nic modules, insmod nic modules, start networking. If ping runs a bit after that, disable autoconfig.

On April 19, 2021 1:06:07 PM EDT, Derek Atkins via Ale <ale at ale.org> wrote:
>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
>
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