ICMPv6 "too-big" packets ignored (filtered ?) by Cloudflare farms

Saku Ytti saku at ytti.fi
Mon Mar 4 19:06:30 UTC 2019


Hey Jean,

>     I confess using IPv6 behind a 6in4 tunnel because the "Business-Class" service
>     of the concerned operator doesn't handle IPv6 yet.
>
>     as such, I realised that, as far as I can figure, ICMPv6 packet "too-big" (rfc 4443)
>     seem to be ignored or filtered at ~60% of ClouFlare's http farms

Might be related to this:
https://blog.cloudflare.com/path-mtu-discovery-in-practice/

If you run ECMP then the hash algorithms make no guarantees ICMP
messages generated by transit devices reach the correct host.

-- 
  ++ytti



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