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On my parents' network I noticed that ICMP packets larger than 71 bytes do not go though.

  • ping 1.1.1.1 -l 71 (and below) is fine
  • ping 1.1.1.1 -l 72 (and above) fail with Request timed out

I tested this on two different Windows 10 computers, one of them is wired to the router (a TP-LINK Archer C50) and another one is connected via Wi-Fi. In both cases the threshold packet size is the same.

What can be the reason for that?

Firewalls on both computers are disabled, and the Archer C50 firewall is enabled with default settings (which I do not see being configurable). I tried with the firewall ("Stateful Packet Inspection" as they call it) enabled and disabled - same thing.

I also had a look at how Wireshark sees the icmp traffic - I only see ping requests.

EDIT: this happens starting from the IP of my gateway (= the fist IP after my router). Pinging either my computer or my router is OK.

  • What happens if you ping the private IP address of your router? What happens if you ping the first hop address on the ISP's end of your broadband link? – Spiff Feb 12 at 22:25
  • @Spiff: I updated the question with your remark. This behaviour starts at the IP of the gateway (my computer and my router are OK) – WoJ Feb 13 at 10:14

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