Nov 22, 2009
Feb 15, 2018 Define Firebox Global Settings - WatchGuard Host Unreachable Select this check box to allow ICMP Host Unreachable messages. Your network usually sends these messages when it cannot use a host or service. Port Unreachable Select this check box to allow ICMP Port Unreachable messages. A host or firewall usually sends these messages when a network service is not available or is not allowed. RFC 792 - Internet Control Message Protocol ICMP Fields: Type 3 Code 0 = net unreachable; 1 = host unreachable; 2 = protocol unreachable; 3 = port unreachable; 4 = fragmentation needed and DF set; 5 = source route failed. Checksum The checksum is the 16-bit ones's complement of the one's complement sum of the ICMP message starting with the ICMP …
Why disabling ICMP unreachables is a bad thing
icmp - Difference between ping timed out and destination The Reply from 192.168.2.120: Destination host unreachable. is after the destination MAC address has timed out of the source/router's ARP cache, and the source/router no longer has, or can get, a MAC address for the destination. Eventually, the destination comes back up, and it responds to the ARP request of the source/router, and your ping is How to Fix This Destination Host Unreachable May 01, 2020
Apr 25, 2013
CCNA 1 v7.0 Curriculum: Module 13 - ICMP Apr 01, 2020 1.1.d (i) ICMP Unreachable, Redirect – Techstat Nov 19, 2017