From: "Toby Corkindale" <toby@dryft.net>

On 16 April 2014 13:00, James Harper <james.harper@bendigoit.com.au> Last time this came up, in 2013, you checked the inbound packets, and reported: "I can confirm what we thought - pings <= 1492 bytes get a response, pings > 1492 bytes get no response, not even a 'fragmentation required'."

Sorry, I did not read all of your conversation before, just remember bits and pieces but it really reminds me of the introduction of a new ADSL router a few months ago. (From my e-mail conversation to the ISP then: --- With the old one[old router], I can ping up to 1464 bytes (ping -s 1464 -D www.zeit.de), above it fails. The new one I can ping just up to 1430 bytes (ping -s 1430 -D www.zeit.de), 1432 is too much. BTW, on the old one I can ping with bigger packets (e.g. 1600 bytes) as long as I allow fragmentation. So, there is something blocking packets bigger than 1430 bytes (ICMP+header), compared to 1464 on the old link. If I have packets above 1464 my end complains (ping: sendto: Message too long) because it knows its own MTU. So the 1430 limit is not on my end, it is further away. .. P.S. After this, I set the MTU at 1458 at the proxy server (not the gateway itself which sits between proxy and the ADSL modem). Then it works. --- I have no access to the ADSL router so I had to report from the device behind it (a FreeBSD router). The ADSL router was doing PPPoE. In-between the technician considered a faulty ADSL router but finally figured out: THe ADSL router had a configuration error (not a hardware problem) I vaguely remember that it had to do with path MTU discovery and blocked ICMP packages further upstream (so the result was not the same on all websites, hence my test with the "reliably failing" www.zeit.de website), as described here: http://en.wikipedia.org/wiki/Path_MTU_Discovery#Problems_with_PMTUD Unfortunately I cannot access the ASDSL router so I do not know exactly what the change in the config was. Regards Peter