ICMP DestinationUnreachable message, code 0x8.
This means that the host that is originating the message is isolated from the network and has no physical interfaces up. For instance if a host detects that it's sole ethernet link is down and it has no other connections (eg, over serial) then that host is considered isolated.
What this message means if it ever exists on the wire is unclear.
No page links to SourceHostIsolated.
