missing hop on traceroute6

classic Classic list List threaded Threaded
1 message Options
Reply | Threaded
Open this post in threaded view
|

missing hop on traceroute6

Maurice Janssen-2
Hi,

I'm seeing some behaviour with traceroute6 that I can't explain.

I have a small home network with a router/firewall running OpenBSD
5.3-stable.  I use pppoe(4) on the WAN interface for IPv4 connectivity.  
For IPv6, I have a gif tunnel from Sixxs.

The gif tunnel has the address 2001:610:600:46b::1 (remote endpoint) and
2001:610:600:46b::2 (local endpoint).  The block 2001:610:637::/48 is
routed towards me.  One of the LAN-interfaces of the router is
configured with 2001:610:637:4::/64.

When I do a traceroute from a local machine to a host somewhere on the
internet, I see all the hops that I expect to see.  For example:

$ traceroute6 -n xs8.xs4all.nl
traceroute6 to xs8.xs4all.nl (2001:888:0:1::888) from
2001:610:637:4::14, 64 hops max, 12 byte packets
  1  2001:610:637:4::1  0.503 ms  0.445 ms  0.459 ms
  2  2001:610:600:46b::1  6.287 ms  5.624 ms  5.59 ms
  3  * * *
  4  2001:610:1:80bb:192:87:102:97  5.983 ms  5.716 ms  5.747 ms
  5  2001:610:f01:9168::169  5.727 ms  5.734 ms  5.75 ms
  6  2001:610:e08:80::81  5.972 ms  19.351 ms  5.865 ms
  7  2001:610:f16:6056::2  5.871 ms  9.22 ms  5.989 ms
  8  2001:888:1:4000::2  6.612 ms  6.236 ms  6.249 ms
  9  2001:888:0:1::888  6.353 ms  6.23 ms  6.24 ms

Hop 1 is my local router, hop 2 is the remote tunnel endpoint.

When doing a traceroute6 in the reverse direction, I get the following
result:
$ traceroute6 -n gemini.z74.net
traceroute to gemini.z74.net (2001:610:637:4::14), 30 hops max, 80 byte
packets
  1  2001:888:0:1::1  0.366 ms  0.457 ms  0.555 ms
  2  2001:888:1:4000::1  0.505 ms  0.490 ms  2.349 ms
  3  2001:610:f16:6056::1  0.466 ms  0.427 ms  0.483 ms
  4  2001:610:f01:9216::218  0.970 ms  0.993 ms  1.006 ms
  5  2001:610:188:994:145:97:20:249  0.883 ms  1.008 ms  0.904 ms
  6  2001:610:1:80bb:192:87:102:107  0.853 ms  0.771 ms  0.792 ms
  7  2001:610:600:46b::1  0.921 ms  0.973 ms  0.855 ms
  8  2001:610:637:4::14  7.014 ms  7.012 ms  6.978 ms

Hop 7 is the remote tunnel endpoint, hop 8 is a system on my home
network.  I would expect to see an additional line between 7 and 8 for
my local router.
Is this expected for a gif tunnel or is there a bug in the TTL handling?

Best regards,
Maurice