www.arin.net

[Alexander Gall]

On Tue, 22 Aug 2006 09:43:30 +0200, Alexander Gall <gall at switch.ch> said:

> 2) Packets exceeding a certain size seem to be dropped on the path
>    from 2001:500:4:1::80 to me, just like Larry has reported in
>    another message in this thread.  For the record, my (incomplete)
>    path towards 2001:500:4:1::80 is

[...]

I think I have located the problem.  Traceroute with 1496 byte packets

traceroute: Warning: Multiple interfaces found; using 2001:620:0:4:203:baff:fe4c:d99b @ bge0:1
traceroute to 2001:500:4:1::80, 30 hops max, 1496 byte packets
 1  swiLM1-V4.switch.ch (2001:620:0:4::1)  1.017 ms
 2  swiNM1-V610.switch.ch (2001:620:0:c047::1)  0.834 ms
 3  swiCS3-G3-3.switch.ch (2001:620:0:c046::1)  0.916 ms
 4  swiCS5-10GE-1-3.switch.ch (2001:620:0:c039::5)  0.938 ms
 5  swiZH2-G2-8.switch.ch (2001:620:0:c016::2)  1.050 ms
 6  swiCE3-10GE-1-1.switch.ch (2001:620:0:c027::1)  4.812 ms
 7  2001:450:2002:10::1  14.540 ms
 8  2001:504:0:2::3549:1  94.030 ms
 9  2001:504:0:2::3549:1  93.922 ms
10  equi6ix-ash.ipv6.us.occaid.net (2001:504:0:2:0:3:71:1)  94.636 ms
11  2001:4830:e6:a::2  95.780 ms
12 ^C

and with 1497 byte packets

traceroute: Warning: Multiple interfaces found; using 2001:620:0:4:203:baff:fe4c:d99b @ bge0:1
traceroute to 2001:500:4:1::80, 30 hops max, 1497 byte packets
 1  swiLM1-V4.switch.ch (2001:620:0:4::1)  1.017 ms
 2  swiNM1-V610.switch.ch (2001:620:0:c047::1)  0.865 ms
 3  swiCS3-G3-3.switch.ch (2001:620:0:c046::1)  0.925 ms
 4  swiCS5-10GE-1-3.switch.ch (2001:620:0:c039::5)  0.949 ms
 5  swiZH2-G2-8.switch.ch (2001:620:0:c016::2)  1.063 ms
 6  swiCE3-10GE-1-1.switch.ch (2001:620:0:c027::1)  5.077 ms
 7  2001:450:2002:10::1  14.610 ms
 8  *
 9 ^C

I checked with source routing (yes, this still works in IPv6 and it's
wonderful for debugging!) that the path is symmetrical.  My guess is
that there is an MTU mismatch on the interconnection between GBLX and
Equinix (probably a tunnel).

--
Alex