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Monitoring/check conntrack

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check_conntrack is an Icinga check that ensures that the nf_conntrack table is not full.

Things to do

  • Check if the sysctl net.netfilter.nf_conntrack_tcp_timeout_time_wait is correctly set to 65, there's a race connection which sometimes make it apply the 120 seconds default:

https://phabricator.wikimedia.org/T136094. If that's the case, reset it to 65: "sysctl -w net.netfilter.nf_conntrack_tcp_timeout_time_wait=65"

  • check the relevant "max" value: cat /proc/sys/net/netfilter/nf_conntrack_max
  • check the current count: cat /proc/sys/net/netfilter/nf_conntrack_count
  • raise the max value: echo 524288 > /proc/sys/net/netfilter/nf_conntrack_max