Package: nagios-plugins Version: 2.2-3 If the remote host has an IPv6 address configured, the check_ping plugin seems to do an ICMPv6 check, even when we use -4 to force IPv4.
You can reproduce by doing a check_ping -4 $ /usr/lib/nagios/plugins/check_ping -4 -H www.sysnove.net -w 1000,100% -c 2000,100% -p 1 PING OK - Paquets perdus = 0%, RTA = 1.36 ms|rta=1.364000ms;1000.000000;2000.000000;0.000000 pl=0%;100;100;0 while monitoring the network with tcpdump. $ sudo tcpdump -i any dst 2001:bc8:3977:802::1 and icmp6 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes 09:58:34.772859 IP6 infra-mon04.sysnove.net > sysnove-www01.sysnove.net: ICMP6, echo request, seq 1, length 64 I'm using an up to date Debian 9.6 with nagios-plugins 2.2-3. This problem is not present on 8.11 with nagios-plugins 2.1.1-1. -- Guillaume Subiron Mail - maet...@subiron.org GPG - 5BC2 EADB MSTDN - @maet...@mstdn.fr IRC - maethor@(freenode|geeknode)