Host unreachable (no route)

What it usually means

There was no network route to the host at all. Usually a firewall rule, a withdrawn route, or a server that is switched off.

What to check first

• The server is switched on and its network interface is up (cloud console, hosting panel).
• A firewall or security group rule was not changed to block all inbound traffic.
• A route or IP address was not withdrawn: a changed floating IP or a cancelled server behaves exactly like this.

How ErrorDetector reports it

This is a reachability failure. The check is repeated immediately to rule out a blip; once confirmed, an incident opens with this cause on it, every channel on the monitor is alerted, and the outage counts against uptime until the next successful check closes the incident.

Caught by: httpkeywordapipingportdns monitors. Read about the incident management feature.