On 2011-06-01T18:07:26-0300, Henrique de Moraes Holschuh <hmh@debian.org> wrote:
> On Wed, 01 Jun 2011, Gerald Turner wrote:
> > Henrique de Moraes Holschuh <hmh@debian.org> writes:
> > $ tracepath6 schein.debian.org
> > 1?: [LOCALHOST] 0.031ms pmtu 1480
> > 1: shub-niggurath.unzane.com 0.162ms
> > 1: shub-niggurath.unzane.com 0.360ms
> > 2: gturner-1.tunnel.tserv14.sea1.ipv6.he.net 6.576ms
> > 3: gige-g2-6.core1.sea1.he.net 5.654ms
> > 4: 10gigabitethernet9-1.core1.sjc2.he.net 26.522ms
> > 5: 10gigabitethernet3-2.core1.pao1.he.net 34.657ms
> > 6: he.pao1.isc.org 29.855ms
> > 7: int-0-0-0.r1.sjc3.isc.org 31.418ms asymm 5
> > 8: schein.debian.org 27.519ms reached
> > Resume: pmtu 1480 hops 8 back 59
>
> 8 hops to get to shein, and *59* hops to get back?!
>
> That path is hopelessly broken. In fact, this is so weird I'd guess
> something is screwing up the TTL fields in the way.
That's usual. Most of the "back" numbers reported by tracepath and
tracepath6 are in the vicinity of 59, yet this causes no breakage
elsewhere. I even have a "back 59" to shub-niggurath.unzane.com from
another he.net IPv6 tunnel:
% tracepath6 shub-niggurath.unzane.com
1?: [LOCALHOST] 0.091ms pmtu 1480
1: kenyon.tunnel.tserv3.fmt2.ipv6.he.net 31.427ms
1: kenyon.tunnel.tserv3.fmt2.ipv6.he.net 31.832ms
2: gige-g5-19.core1.fmt2.he.net 26.653ms
3: 10gigabitethernet1-1.core1.sjc2.he.net 23.876ms
4: 10gigabitethernet4-3.core1.sea1.he.net 49.969ms
5: 2001:470:0:9b::2 46.620ms
6: shub-niggurath.unzane.com 50.540ms reached
Resume: pmtu 1480 hops 6 back 59
Another example on native IPv6 (I receive mail on IPv6 just fine from
liszt.debian.org):
% tracepath6 liszt.debian.org
1?: [LOCALHOST] 0.022ms pmtu 1500
1: 2600:3c01:ffff:0:ca4c:75ff:fef5:d63f 0.541ms
1: 2600:3c01:ffff:0:ca4c:75ff:fef5:d63f 0.481ms
2: 10gigabitethernet2-3.core1.fmt1.he.net 6.630ms
3: 10gigabitethernet1-2.core1.sjc2.he.net 0.947ms
4: 10gigabitethernet3-3.core1.den1.he.net 28.013ms
5: 10gigabitethernet1-1.core1.chi1.he.net 61.588ms
6: 10gigabitethernet7-2.core1.nyc4.he.net 71.757ms
7: 10gigabitethernet3-3.core1.lon1.he.net 136.335ms
8: 10gigabitethernet1-1.core1.ams1.he.net 144.150ms
9: ge-0-0-0.peer1.ams.man-da.net 145.886ms asymm 10
10: ge-0-1-4-400.core1.fra1.ix.f.man-da.net 149.567ms asymm 11
11: ge-2-0-4-400.core1.rz.hda.da.man-da.net 150.975ms asymm 13
12: te-2-3-0-403.core1.sm.tu.da.man-da.net 150.295ms
13: ge-0-2-400.cust1.sm.tu.da.man-da.net 151.566ms asymm 12
14: fw01-man-da.ayous.org 150.839ms asymm 13
15: liszt.debian.org 152.388ms reached
Resume: pmtu 1500 hops 15 back 51
--
Kenyon Ralph
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