SixXS::Sunset 2017-06-06

Ticket ID: SIXXS #1282467
Ticket Status: User

PoP: noosl01 - Availo (Oslo)

Path MTU discovery + hop limit exceeded problems from noosl1
[no] Shadow Hawkins on Thursday, 03 December 2009 00:35:49
Hello, My tunnel containing 2001:16d8:ee1c::/48 seems to have two problems that may or may not be related. First: Path MTU discovery from the outside (2001:700:300:1880::2, for instance) is broken. I'm SSH-ing to a host (from which I have working connectivity to from several different places around the world), and when I'm trying to connect to my screen the connection freezes. tcpdump on the sender shows the machine sending packets like this: 00:25:13.209037 IP6 2001:700:300:1880::2.22 > 2001:16d8:ee1c:0:213:2ff:feaa:9cd8.48591: . 1891122625:1891124053(1428) ack 2699540521 win 107 <nop,nop,timestamp 650949801 4294933753> However, the receiving router sees no such packets on its sixxs interface, and no ICMPv6 Packet Too Big packets are returned either. Second, the PoP seems to have a routing loop somewhere. For instance, ping6 www.sixxs.net gives: PING www.sixxs.net(noc.sixxs.net) 56 data bytes From 2001:16d8:1:1334::69 icmp_seq=1 Time exceeded: Hop limit From 2001:16d8:1:1334::69 icmp_seq=2 Time exceeded: Hop limit From 2001:16d8:1:1334::69 icmp_seq=3 Time exceeded: Hop limit and a tracepath6 shows: fugl:~> tracepath6 www.sixxs.net 1?: [LOCALHOST] pmtu 1500 1: 2001:16d8:ee1c::1 2.305ms 1: 2001:16d8:ee1c::1 2.354ms 2: 2001:16d8:ee1c::1 2.247ms pmtu 1280 2: gw-46.osl-01.no.sixxs.net 5.450ms 2: gw-46.osl-01.no.sixxs.net 5.357ms 3: 2002-sixxs.cr0-r23.ver-osl.no.ip6.p80.net 5.880ms 4: no reply 5: 2001:16d8:1:1334::65 20.604ms asymm 3 6: no reply 7: 2001:16d8:1:1334::65 21.947ms asymm 3 8: no reply 9: 2001:16d8:1:1334::65 29.863ms asymm 3 10: 2001:16d8:1:1334::69 34.915ms asymm 4 11: 2001:16d8:1:1334::65 35.705ms asymm 3 12: 2001:16d8:1:1334::69 41.789ms asymm 4 13: 2001:16d8:1:1334::65 41.816ms asymm 3 14: 2001:16d8:1:1334::69 48.922ms asymm 4 15: 2001:16d8:1:1334::65 48.960ms asymm 3 16: 2001:16d8:1:1334::69 56.502ms asymm 4 17: 2001:16d8:1:1334::65 56.415ms asymm 3 ^C This may or may not be the reason for the ICMPv6 Packet Too Big packets not coming back. Could you please take a look?
State change: user Locked
[ch] Jeroen Massar SixXS Staff on Thursday, 03 December 2009 09:13:29
Message is Locked
The state of this ticket has been changed to user
Path MTU discovery + hop limit exceeded problems from noosl1
[ch] Jeroen Massar SixXS Staff on Thursday, 03 December 2009 09:15:02
Tracepath6 seems to reveal an 1500 MTU path to the given host. Can reach noc just fine from there, maybe a temporary issue? Results here, one can also create these using the distributed traceroute tool. tracepath6 2001:700:300:1880::2 1?: [LOCALHOST] pmtu 1500 1: 2002-sixxs.cr0-r23.ver-osl.no.ip6.p80.net 0.663ms 1: 2002-sixxs.cr0-r23.ver-osl.no.ip6.p80.net 0.685ms 2: 2001:16d8:1:1334::69 7.714ms 3: v1315-r69.cr0-r84.kn1-sto.se.ip6.p80.net 7.711ms 4: mtu4470.ge-b.netnod.nordu.net 8.462ms asymm 5 5: se-tug.nordu.net 8.952ms asymm 6 6: oslo-gw.uninett.no 250.051ms asymm 7 7: trd-gw1.uninett.no 22.940ms asymm 8 8: ntnu-gsw.ntnu.no 23.196ms 9: hb-gsw.ntnu.no 23.201ms 10: pannekake.samfundet.no 22.695ms reached Resume: pmtu 1500 hops 10 back 55 traceroute to noc.sixxs.net (2001:838:1:1:210:dcff:fe20:7c7c) from 2001:16d8:aaaa:4::2, 30 hops max, 16 byte packets 1 2002-sixxs.cr0-r23.ver-osl.no.ip6.p80.net (2001:16d8:aaaa:4::1) 0.291 ms 0.441 ms 0.239 ms 2 2001:16d8:1:1334::69 (2001:16d8:1:1334::69) 7.477 ms 7.473 ms 7.484 ms 3 v1315-r69.cr0-r84.kn1-sto.se.ip6.p80.net (2001:16d8:1:1315::84) 7.476 ms 7.436 ms 7.481 ms 4 v1317-r84.cr0-r73.gbl-mlm.se.ip6.p80.net (2001:16d8:1:1317::73) 14.467 ms 14.456 ms 14.224 ms 5 v1306-r73.cr0-r72.gbl-cph.dk.ip6.p80.net (2001:16d8:1:1306::72) 14.97 ms 14.961 ms 14.976 ms 6 v1308-r72.cr0-r70.tc2-ams.nl.ip6.p80.net (2001:16d8:1:1308::70) 25.964 ms 25.972 ms 25.949 ms 7 ams-ix2.ipv6.concepts.nl (2001:7f8:1::a501:2871:2) 26.463 ms 26.443 ms 26.969 ms 8 2001:838:5:2::1 (2001:838:5:2::1) 26.458 ms 26.454 ms 26.469 ms 9 2001:838:5:a::2 (2001:838:5:a::2) 28.211 ms 28.443 ms 28.23 ms 10 noc.sixxs.net (2001:838:1:1:210:dcff:fe20:7c7c) 27.961 ms 27.955 ms 27.964 ms

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