libxt_connlimit.man revision 18c475d7040abc6d3094ee0348904deafe997508 
1Allows you to restrict the number of parallel connections to a server per
2client IP address (or client address block).
3.TP
4[\fB!\fP] \fB\-\-connlimit\-above\fP \fIn\fP
5Match if the number of existing connections is (not) above \fIn\fR.
6.TP
7\fB\-\-connlimit\-mask\fP \fIprefix_length\fP
8Group hosts using the prefix length. For IPv4, this must be a number between
9(including) 0 and 32. For IPv6, between 0 and 128.
10.P
11Examples:
12.TP
13# allow 2 telnet connections per client host
14iptables \-A INPUT \-p tcp \-\-syn \-\-dport 23 \-m connlimit \-\-connlimit\-above 2 \-j REJECT
15.TP
16# you can also match the other way around:
17iptables \-A INPUT \-p tcp \-\-syn \-\-dport 23 \-m connlimit ! \-\-connlimit\-above 2 \-j ACCEPT
18.TP
19# limit the number of parallel HTTP requests to 16 per class C sized \
20network (24 bit netmask)
21iptables \-p tcp \-\-syn \-\-dport 80 \-m connlimit \-\-connlimit\-above 16
22\-\-connlimit\-mask 24 \-j REJECT
23.TP
24# limit the number of parallel HTTP requests to 16 for the link local network
25(ipv6)
26ip6tables \-p tcp \-\-syn \-\-dport 80 \-s fe80::/64 \-m connlimit \-\-connlimit\-above
2716 \-\-connlimit\-mask 64 \-j REJECT
28