I have an app that runs a ping test from a networks primary mx wan 1 to every other sites primary wan1 and gives me the results.
(the ping test works in tow API calls, a post to ask it to do the tests and then a get to retrieve the results)
For lots of sites it works fine. A few sites have 100% packet loss which is due to firewalls....but some sites return a result saying all the ping tests were received and were successful, but then the api response does not contain the actual latency data. So I just know that 5 out of 5 pings were successful, but no idea what the times were.
If I do the ping from the meraki dashboard GUI tool - the pings work properly.
I spoke to meraki support who said the dashboard works because the ping tool doesn't go out to open internet but travels inside some secure network. - The api problem must be due to the local ISP's filtering the traffic.
But I don't understand what kind of filtering can allow a packet through but somehow strips the packet of certain data? Is that a real thing?
The ID and sequence number are in the ICMP header, if they were stripped then the requesting device would not be able to match up the reply (so the ping would fail), can't see there's much else to strip.
Can you try a packet capture on one of the affected interfaces, maybe it'll shed some light on differences between sites?
Tbh it sounds like a bug to me, if the ping succeeds it means the device that sent the echo request has received a matching echo reply, so it should be able to calculate the time difference.