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There are four tables and five chains in iptables concept. All the tables:raw,filter,nat,mangle;and the chains:input,output,forward,prerouting,postrouting.
The diagram below shows the flow of packets through the chains in various tables in detail.
The diagram below shows the flow of packets through the chains in various tables:
Let's have a look at output chain (same as in prerouting chain),it says from right to left that raw,connecting tracking,mangle,nat,filter,is connecting tracking a kind of table? A conclusion in the webpage says Each of these tables are composed of a few default chains,so from this conclusion, i think that connecting tracking is a kind of table.

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It's not an iptables-"table", but a module making use of the linux kernel functionality of connection tracking, which stores connection information in /proc/net/ip_conntrack and/ or /proc/net/nf_conntrack.

| improve this answer | |
  • cat /proc/net/ip_conntrack cat: /proc/net/ip_conntrack: No such file or directory – scrapy Sep 2 '19 at 14:36
  • Did you load the conntrack module? modprobe nf_conntrack – Lenniey Sep 2 '19 at 14:39
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    It is /proc/net/nf_conntrack ,instead of /proc/net/ip_conntrack in my centos7. – scrapy Sep 2 '19 at 14:42
  • I'll edit my answer, depends on the version. – Lenniey Sep 2 '19 at 14:47

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