Sends to addresses no card has on the new arp-routed network (ping on the
LAN and behind a router, two UDP datagrams, one behind a failing one):
frames and calls. ScenarioNetwork builds routers and their interfaces.
Measured: ARP asks twice, a round trip each, then host unreachable; the
thread that waits is the ping's caller, the router's IP thread, or the
node's transport thread per protocol, which blocks the next send.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
