Re: How long is reasonable to fix a routing issue in IPv6?

[Jared Mauch <jared () puck nether net>]

If those interim hops are IPv4 only nodes part of 6/PE there could be a few things going on here.

1) Juniper u-RPF for family inet6 drops the mapped-v4-v6 source packets generated by a P/PE router
2) FreeBSD (8.2 at least) doesn't seem to like mapped-v4-v6 source packets with its default traceroute (same for mtr on 
FreeBSD)
(tcpdump will show you the packets coming back, the freebsd traceroute6 seems to have a few unresolved bugs.. you need 
to force -w 1 as well likely)
3) If end-to-end connectivity works, 

Workarounds:

the IPv4 only P/PE device should have some sort of IPv6 address placed on transit interfaces to allow TTL expired to be 
sourced from something capable (this IP doesn't need to be able to be reached/routed to that interface, just exist).

I spent a lot of time looking at a similar problem and it ended up being a combination of #1 & #2 above.  You will see 
this problem across The AT&T and Cogent networks in my experience.

- Jared

On Jul 6, 2011, at 10:39 PM, Mark Andrews wrote:

> The below has been on going for over a week (yes it has been reported to HE)
> and the IETF).
>
> Not returning time exceeded really make debugging routing problems hard.
>
> Mark
>
> traceroute6 -lI www.ietf.org
> traceroute6 to www.ietf.org (2001:1890:1112:1::1e) from 2001:470:1f00:ffff::5a1, 64 hops max, 16 byte packets
> 1  dviscorg.tunnel.tserv1.fmt.ipv6.he.net (2001:470:1f00:ffff::5a0)  172.669 ms  182.219 ms  170.424 ms
> 2  2001:470:0:1f::1 (2001:470:0:1f::1)  178.128 ms  171.926 ms  174.877 ms
> 3  gige-g4-8.core1.fmt2.he.net (2001:470:0:2d::2)  172.193 ms  171.265 ms  171.221 ms
> 4  10gigabitethernet6-4.core1.lax1.he.net (2001:470:0:18d::2)  198.338 ms  190.680 ms  182.413 ms
> 5  10gigabitethernet1-3.core1.lax2.he.net (2001:470:0:72::2)  178.924 ms  189.431 ms  180.538 ms
> 6  2001:470:0:1e6::2 (2001:470:0:1e6::2)  181.137 ms  179.374 ms  182.321 ms
> 7  * * *
> 8  * * *
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> 12  2001:1890:1fff:ffff::1 (2001:1890:1fff:ffff::1)  262.713 ms * *
> 13  * * *
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>
> -- 
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE:        +61 2 9871 4742                  INTERNET: marka () isc org