[j-nsp] Strange ARP issue on M7i

Tobias Heister lists at tobias-heister.de
Tue Aug 14 16:00:12 EDT 2012


Am 14.08.2012 15:12, schrieb Markus:
> Isn't that weird? Where did that arp entry come from and why was it saved on the Juniper for so long, and only got removed after I removed the static routing of that /24?

We saw a similar thing a short time ago on an MX480 running 10.4R9
In our case it was a bgp route pointing to a no longer existing ip address as the next-hop. The arp entry for this ip address stayed active as long as there was an active route for it.
Even clearing the arp cache witch clear arp hostname x.x.x.x did not do the trick. The next-hop ip was gone for several weeks and the arp entry had low timeout values left but never expired.
After clearing the route the arp entry vanished as expected.

I guess something keeps the arp entry from being deleted as long as there are or were forwarding entries in the fib for it at any time.

Kind Regards
Tobias Heister

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