The ICMP Destination Unreachable message is sent by a router in response to a packet which it cannot forward because the destination (or next hop) is unreachable or a service is unavailable. Examples of such cases include a message addressed to a host which is not there and therefore does not respond to ARP requests, and messages addressed to
Ping 192.168.56.101 from the host is OK though. I try to gain some hints by capturing packets on the VirualBox-Host-Only-Network adapter with wireshark. And I see some ICMP packets sent from 192.168.56.101 to 192.168.56.1 which tell me "Destination unreachable … ICMP Destination Unreachable (Type 3) Flood | MazeBolt ICMP Destination Unreachable (Type 3) Flood. ICMP Floods are DDoS attacks aimed at consuming computing power and saturating bandwidth. ICMP Floods are generally spoofed attacks and normally come at a very high rate. Time Exceeded ICMP Floods, if not dropped by DDoS mitigation devices on the perimeter, may overwhelm the internal network architecture. Internet Control Message Protocol - Wikipedia タイプ=3、コード=4のICMPパケットをファイアウォール等でフィルタしてしまうと、経路MTU探索ブラックホールと呼ばれる問題が発生する。 また、RFC 792 (ICMPプロトコル本体の)Destination Unreachable Messageをみると次HopのMTUの項目はなく、未使用のみとなっている。
タイプ=3、コード=4のICMPパケットをファイアウォール等でフィルタしてしまうと、経路MTU探索ブラックホールと呼ばれる問題が発生する。 また、RFC 792 (ICMPプロトコル本体の)Destination Unreachable Messageをみると次HopのMTUの項目はなく、未使用のみとなっている。
cisco - Telnet - "Destination unreachable" response The Destination Unreachable message is an ICMP Type 3 message. ICMP can also further divide the different types into various "codes". The Port Unreachable message is an ICMP Type 3 Code 3 Message. This response is the idealistic, "early days of the Internet" suggest response. Back when the Internet was a trustworthy place, this was very helpful.
iptables - Destination unreachable (Host administratively
How to Solve Destination Net Unreachable - Ping Error Message Time Warner email started having a stroke, and I did a PING which resulted in, "Request timed out." I did a TRACERT which resulted in, "13 * * 75.180.131.161 reports: Destination net unreachable."