claudebox-firewall.sh drops everything from a box to the host except
DNS (53) and DHCP (67); ICMP to 10.87.0.1 dies in that trailing drop on
every healthy host. The doctor used exactly that ping as its routing
probe, so it reported 'cannot even reach the gateway' — and a NOT-fit-
to-drill verdict — on a host whose very next line proved DNS working
through that same gateway.
Probe routing the way the contract states it: a box reaches the public
internet. curl to 1.1.1.1 by address, reusing the one probe for the
DNS-failure diagnosis instead of running it twice.
