ICMPv6 rate limits breaking PMTUD (and traceroute) [Re: Comcast enables 6to4 relays]
Pekka Savola
pekkas at netcore.fi
Thu Sep 2 05:57:20 UTC 2010
On Wed, 1 Sep 2010, Simon Leinen wrote:
> Note that the same rate-limit will also cause stars in IPv6 traceroutes
> through popular routers if the default setting is used.
...
> Anybody knows which defaults are used by other devices/vendors?
I've noticed 6to4 relay rate-limiter blackholes before (e.g. in
Your.org relay in AMS, got quickly fixed once I reported it).
FWIW, Linux default is 1000pps and BSD has 100pps which is too low for
a popular relay. In our relays we've used 1000-3000pps.
The majority of ICMPv6's is caused by windows boxes testing the
relay's liveness.
Depending on the MTU configuration of the relay's tunnel interface
(there isn't a BCP on this I think), you will also get more issues if
you run the relay at MTU=1280 rather than (say) 1480. But using 1480
may result in an IPv4 blackhole if you source packets from an anycast
address and your destination is e.g. behind PPPoE, so...
--
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
More information about the NANOG
mailing list