What does ICMP type 3 mean?
port unreachableICMP error messages of Type: 3 represent a "destination unreachable" situation, where code values clarify the type of unreachability, as follows: 0 = net unreachable; 1 = host unreachable; 2 = protocol unreachable; 3 = port unreachable; 4 = fragmentation needed and DF is set; 5 = source route failed.
What are the ICMP type and code numbers?
Internet Control Message Protocol (ICMP) ParametersType 0 — Echo Reply.Type 1 — Unassigned.Type 2 — Unassigned.Type 3 — Destination Unreachable.Type 4 — Source Quench (Deprecated)Type 5 — Redirect.Type 6 — Alternate Host Address (Deprecated)Type 7 — Unassigned.More items...•
What is an ICMP code?
ICMP (Internet Control Message Protocol) is a network protocol used for diagnostics and network management. A good example is the “ping” utility which uses an ICMP request and ICMP reply message. When a certain host of port is unreachable, ICMP might send an error message to the source.
What does ICMP type 11 code 0 denote?
Explanation: An ICMP Type 11, Code 0 means Time Exceeded [RFC792], Code 0 = Time to Live exceeded in Transit and Code 1 = Fragment Reassembly Time Exceeded.
Which ICMP types allow?
The only essential ICMP traffic you need to allow in and out of your firewall is Type 3 and Type 4. Everything else is either optional or should be blocked.
What is the type code for an ICMP echo request?
Echo and Echo-Reply An echo packet has type 8 set in the ICMP header, and the reply uses type zero. Neither have any codes defined, so the code field in the header is always set to zero.
Which three types of ICMP messages are common to both ICMPv4 and ICMPv6?
ICMP messages common to both ICMPv4 and ICMPv6 include: Host confirmation....0 - net unreachable. host unreachable. protocol unreachable. port unreachable.