ICMP Type: 8, Code: 255(?)
I'm attempting to fine-tune our ICMP policies. An ISP is reporting that their IPv4 ICMP Ping Test has failed despite me using the default packet filter Ping policy (type:8, code: 255) and allowing their address blocks to hit our client's external addresses. However their suggested way of testing the connection via their website reports that the ping test are actually successful. Regardless I went down the rabbit hole of ICMP types and codes.
Would I potentially also need to allow Ping type 0 for echo reply or is that unnecessary?
For Type 8 - what does "code: 255" define? From the above IANA link, there doesn't seem to be any code for ICMP Type 8?