Suppose there are always packets being processed in iptables chains all the time.

When I update iptables rules vi command line, would those packets still in process be dropped or delayed?

In other words, are iptables operations atomic?

  • do not cross-post the same question over SE sites, please
    – Serge
    Jun 4, 2016 at 4:42

1 Answer 1


If you're worried about a specific packet that is currently transiting, half way through the routing system, the impact is impossible to predict, but the next packet that matches the rule will be filtered appropriately.

The packet will obviously continue its route much faster than you could press Enter. So in the bottom line, worrying about this is really a waste of time if you add the proper filtering rules. The only way to do it better would imply having a time machine.

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