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Re: Question about NetBSD implementation of IPv6 SLAAC and RFC4941



On 06/04/2020 21:25, Christos Zoulas wrote:


On Apr 5, 2020, at 9:35 PM, Roy Marples <roy%marples.name@localhost> wrote:

Ah, now we are getting interesting! So, some questions:

1) Are you soliciting a router or just waiting for an RA to magically appear?
   This is fairly important as recent RFC 7772 vastly reduces broadcasts to the
   network - it unicasts a lot more than it broadcasts - and makes each node
   wanting a router actually solicit one.
   If you're not using dhcpcd to solicit, what are you using?

I am not doing anything special. I just set ip6mode=autohost in rc.conf which does:

                 /sbin/sysctl -qw net.inet6.ip6.accept_rtadv=1

and I am all set.

The default maximum time from one RA to the next without solicition is 600 seconds, the upport limit is 1800 seconds.

Now, if your IPv6 routers don't support RFC 7772 and there are many IPv6 nodes soliciting a RA (you'll get a RA every 3 seconds or so) or are configured with a low MaxRtrAdvInterval then that explains why it "works" for you.

Given an IPv6 router which supports RFC 7772, I wouldn't want to wait 10 minutes (default, max 30 minutes) after userland has booted before network connectivity comes up (assuming IPv6 is required for connectivity). And frankly if anyone submitted a bug report for this I would just tell them to solicit a RA because that's how IPv6 is designed.

Is this something we want to support?

Roy


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