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I need to ensure on my server that maximum new ssh connections per minute are not more then 5.

sudo /sbin/iptables -A INPUT -p tcp --syn --dport 22 -m connlimit --connlimit-above 5 -j REJECT

Above IPtables rule work for me, but it will not allow new connections after one minute.

Any pointers how to achieve this?

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up vote 3 down vote accepted

Add --reject-with tcp-reset so that the rejected connections get closed gracefully otherwise you're going to have a bunch of SYN_WAITs sitting around.

sudo /sbin/iptables -A INPUT -p tcp --syn --dport 22 -m connlimit --connlimit-above 5 -j REJECT --reject-with tcp-reset
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