IPv6 issues (ICMP type 2 / black holes)

A technical one this --- I'm seeing issues with the EE network on IPv6 where I do not get 'packet too big' messages from the network.

I've tried to capture more detail and test + result in a github repo - comments appreciated

https://github.com/planetf1/bt-ee-ipv6-blackhole

Basically a mtu of 1500 is fine for some sites (for example x.ai, cloudflare, apple) but fails for others (gcp, aws). This in itself is fine/normal. However not getting any response (ie black hole) is unexpected and crazily annoying! (are other ISPs better?)

Edited by planetf1 (Tue 03-Mar-26 22:51:39)