Why does blocking ICMP cause constant Orbi reboots?

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F_V wrote:

My question is this:  Why does this Orbi not allow you to block ICMP between the router and the firewall/gateway appliance?  If I allow ICMP, it works as expected, but as soon as I block ICMP traffic, the Orbi just reboots constantly, making it impossible to connect for more than a few seconds.  Does blocking ICMP tell the Orbi that it's offline and cause constant reboots?

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I have been out of touch and just came across this post.  My guess is that your analysis is exactly correct.  Some time sensitive routine inside the Orbi RBRE960 periodically uses ICMP to verify that "something" is there on the WAN interface.  i.e., it is "connected".  It is fairly clear that the physical Ethernet connection being "up" is not enough.  I would venture to guess that the Orbi is looking for either:

• The device which assigned an IP address to the Orbi using DHCP, or
• Some specific resource on the internet, such as a DNS server or even Netgear itself.

"Oh, crap. The DHCP server that gave me an IP is no longer "THERE". I better start over."

This would not happen when the Orbi is  in router mode because Orbi can function perfectly well as a stand-along network with no connection to the outside world.  (Not particularly useful to most of us, but adequate for specific needs.)

Notice on the web admin Basic tab, the option to "Test" the internet connection:

How about using the pfSense to capture traffic from the Orbi WAN port.  This would reveal what the Test function is doing (in router mode), and might also reveal what address the Orbi is attempting to Ping in Access Point mode.