Ping timeout when pinging in less than 500ms intervals

Installing and Using OpenWrt
1

Hi guys

i have a little issue with my Router running latest OpenWRT.

When i am pinging it (or linux device) with less that half o a seconds intervals, some pings respond with timeouts. Lets say it is around 30% of the pings cannot get back to me.

While the interval is 1 second all is fine.

Do you know how to resolve the issue?

Thank you.

2

Past that you shouldn’t be pinging anything at high rates, you mean?

Check for rate-limit firewall rules. What you’re trying to do looks a lot like a DoS attack.

3

It is just a simple script to fsst ping router 4 times, then my modem, then internet, just to check if all works fine. Otherwise i would have to wait 12 second to finish the task.

Are you saying that router not responding is some sort of DoS attack prevention?

4

High-rate ICMP may be considered as an incoming DoS threat and blocked by the firewall and/or TCP stack.

(Edit: since you said "When i am pinging it (or linux device)" I am assuming it is a general, Linux issue beyond hammering a low-end router's SoC too hard.)

Reordering your script might make sense if execution time is an issue. For example

  • Ping "Internet" at normal rate, three times
    • Return "success" on first ping returned (typically under 1 sec elapsed)
  • If fails all three (4 seconds in now), then try the modem
  • If fails all three (4 seconds in now), then try the router

It's hard to imagine a situation where you can't reach your router or your modem but can reach the Internet, with a single link.

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