[j-nsp] Interesting EX4200 gotcha and "resolution"

[Jeff Wheeler]

On Mon, Sep 26, 2011 at 1:39 PM, Brent Jones <brent at servuhome.net> wrote:
> Did you observe any strange entries in /var/log/shadow when these events occur?
> I've had similar issues, where some EX4200's in a VC lose the ARP
> table, and traffic cannot transit the switch to another switch (if the
> traffic must go through that VCP).
> JTAC was unable to find any root cause, but there were number errors
> in /var/log/shadow about the ASIC forwarding table didn't match what
> was in software/memory

No, the only entries present in /var/log/shadow.log are the mysterious
"Non RTG error" messages that it logs every ~5.5 minutes.

In this instance, the VC contains two EX4200-48T and both switches
have identical halp-nh arp-table data, with both missing the same
entries.

What the root cause is, who knows; but if Juniper wanted to provide me
with a "fix" they could make "clear arp" actually clear the arp
entries.  This happens so rarely that it's only a problem because the
obvious fix that NOC guys try before escalating does not work.

I am hoping a future instance of this problem will get escalated to me
so I can try installing a static ARP entry with a different MAC and
then removing it, which should correct the problem without impacting
other machines on the subnet.

-- 
Jeff S Wheeler <jsw at inconcepts.biz>
Sr Network Operator  /  Innovative Network Concepts