[BUG] All ARP records associated with a router are immediately closed when there is a short ICMP echo packet loss about nav HOT 4 CLOSED

Although the current behavior is undesirable, it is likely still desirable for NAV to close ARP records after a netbox has been down for a while, since we can no longer verify those records by polling the netbox.

The question is: When is it acceptable to close ARP records associated with a "dead" netbox? Some suggestions:

1. It could be acceptable to close them when the netbox is actually declared down by a new boxState entry in alerthist. This happens after 4 minutes of unresponsiveness (by default, configured in eventengine.conf).
2. We might want to wait even longer, in which case it would not be achievable through a database rule. We might instead want to add a new subcommand to the navclean program that will close open ARP records for netboxes that have been down for any number of minutes. The limit could then be configurable on each NAV site (the dbclean cron job runs by default every 5 minutes)

from nav.

I would have to say that I'm leaning towards the latter solution, with some default value provided by NAV. ARP collection runs every 30 minutes by default, so a sensible default could be to close ARP records for devices that have been down for longer than this.

from nav.

This was supposed to be fixed by #2913, but this PR managed to delete the incorrect database rule. The target rule to delete was netbox_status_close_arp, but instead the schema changes delete netbox_close_arp, which is responsible for closing ARP records when a router is deleted from NAV - which is entirely different.

from nav.

Fixed by #2928 - expected in a 5.10.2 release

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