ICMP Errors

https://datatracker.ietf.org/doc/html/rfc792

Here are the main ICMP error types (the ones that indicate problems):

Type Message Code values

3 Destination Unreachable 0 = Net unreachable

1 = Host unreachable

2 = Protocol unreachable

3 = Port unreachable

4 = Fragmentation needed (DF set)

5 = Source route failed

6 = Destination network unknown

7 = Destination host unknown

9 = Network administratively prohibited

10 = Host administratively prohibited

13 = Communication administratively prohibited

4 Source Quench (deprecated) Always 0

5 Redirect 0 = Redirect datagram for the network

1 = Redirect datagram for the host

2 = Redirect for TOS and network

3 = Redirect for TOS and host

11 Time Exceeded 0 = TTL exceeded in transit

1 = Fragment reassembly time exceeded

12 Parameter Problem 0 = Pointer indicates the error

1 = Missing required option

2 = Bad length