DOKK / manpages / debian 12 / icmpinfo / icmpinfo.8.en
ICMPINFO(8) System Manager's Manual ICMPINFO(8)

icmpinfo - interpret ICMP messages

icmpinfo [-v[v[v]]] [-n] [-p] [-s] [-l] [-k]

Icmpinfo is a tool for looking at the ICMP messages received on the running host. It can be used to detect and record 'bombs' as well as various network problems.

The output format is as follows (all on one line):

MMM DD HH:MM:SS ICMP_type[sub-type]
< sender_ip [sender_name] > unreach_ip [unreach_name]
sp=source_port dp=dest_port seq=sequence sz=packet_size

In normal operation, icmpinfo will only report on "weird" packets, mainly icmp_unreachable.

Give information about all icmp packets, excepts pings.

Give about pings too (i.e. icmp_echo_reply).

Include an ascii/hex dump of each packet

Avoid name queries - just give IP addresses. (use this option when running unattended on name server hosts (to avoid possible looping))

Avoid port number to service name decoding.

Show the interface ip that received the packet. Useful only if your host has several network interfaces. In this case an '- my_ip [my_name]' is added between the sender and unreach ip and name fields.

Forks and use the syslog(3) facility to record events (recommended use). (root only option).

Kills the background process started with the -l option.

The packet decoding is planned for ICMP Unreachable outputs and might not be significant for all other Icmp types. Output can be shorter when implied by the packet size or the icmp type.

Laurent Demailly <>. Free software.

V1.11 - 28 August 1995 dl's free utilities