Conversation

Notices

1. Embed this notice
   Matthew Garrett (mjg59@nondeterministic.computer)'s status on Sunday, 28-Jan-2024 20:03:42 JST Matthew Garrett

   This is weird - IPv6 is working fine for most of my devices (can ping google.com, for instance). But on *one* device, ICMP packets go out, but no response comes back. If ping a machine I control I can see it generate reply packets, but tcpdump on the router's WAN port shows the outbound ICMP but no replies. Firewall is set to accept all IPv6. Anyone have any ideas?

   • Embed this notice
     John Ripley (jripley@mastodon.social)'s status on Sunday, 28-Jan-2024 20:03:41 JST John Ripley

     in reply to

     @mjg59 Some ISPs have magic TTL values which they use as an obfuscated way to route traffic differently (e.g no caps). Could be it’s accidentally tripping into that.

     clacke likes this.
   • Embed this notice
     Paul_IPv6 (paul_ipv6@infosec.exchange)'s status on Sunday, 28-Jan-2024 20:03:43 JST Paul_IPv6

     in reply to

     @mjg59

     different packet size/MTU by default

     just one guess. i have seen it.

     clacke likes this.
   • Embed this notice
     Matthew Garrett (mjg59@nondeterministic.computer)'s status on Sunday, 28-Jan-2024 20:03:45 JST Matthew Garrett

     in reply to

     • Paul_IPv6

     @paul_ipv6 But why only for this one device?

   • Embed this notice
     Paul_IPv6 (paul_ipv6@infosec.exchange)'s status on Sunday, 28-Jan-2024 20:03:46 JST Paul_IPv6

     in reply to

     @mjg59

     something filtering ICMPv6 and PMTU not working?