IPv6 down in east San Jose

[daverand]

Over the last few days, IPv6 has been... interesting... on this side. Frequent interface glitches are forcing new DHCP6 addresses out, but this morning, that all changed. There was a bounce at 02:22, new IPv6 delegated addresses were handed out, and.. absolutely no IPv6 connectivity. Even pinging the gateway (in my case, the Sonic side is at fe80::4e73:4fff:fe37:248%ix0) fails. There was bursts of connectivity (along with new delegated IPv6 addresses) this morning, but it's back to dead, both inbound and outbound...

[klui]

I am experiencing something similar but not exactly.

Lately I've read posts about IPv6 challenges so I am slowly familiarizing myself with it. I have also experienced my assigned prefix change after a disconnect (disable/re-enable IPv6 on my router) as well as forced client renew. Auto-renewals from my router's DHCPv6 client are fine.

For the past several days I received a /56 prefix and I could ping the DHCPv6 server and recursive DNS servers from my router. In today's experiment I forced a renew but didn't receive another prefix until almost 2 hours later. When I first tried to get a prefix it this weekend it took 30 minutes; yesterday when I disabled and re-enabled IPv6, it took around 20 minutes.

Today when I got the new prefix I could ping the DHCPv6 server but not Sonic's recursive DNS servers.

[klui]

Did some other stuff and I tried pinging the DNS servers just now... and I can ping them.

[daverand]

And, in the continuing IPv6 strangeness, the IA_NA on my public interface was removed:

Jan 9 19:27:51 main10 dhcp6c[98543]: make an IA: NA-0
Jan 9 19:27:51 main10 dhcp6c[98543]: status code for NA-0: no addresses
Jan 9 19:27:51 main10 dhcp6c[98543]: IA NA-0 is invalidated
Jan 9 19:27:51 main10 dhcp6c[98543]: remove an IA: NA-0


IPv6 is still working. The LL gateway (in my case, fe80::4e73:4fff:fe37:248%ix0) still responds. DHCP6 still hands me a
delegation:

Jan 9 19:27:51 main10 dhcp6c[98543]: IA_PD prefix: 2001:5a8:4a81:8a00::/56 pltime=21600 vltime=6305012012128

But things like IPv6 nameserver requests outbound from my router now fail, since the Link-Local address of the interface won't be a reachable address to the Sonic nameservers.

Odd. Very odd.

(oh. And traceroute still shows the gateway responding correctly, but I have no 2001:5a8:5:4072:: IA_NA address on my interface any more:

2 2001:5a8:601:22:: 0.666 ms 1.362 ms 0.621 ms
3 2001:5a8:5:4072::2 5.390 ms 16.282 ms 4.692 ms
4 ae2.cr4.snjsca11.sonic.net 1.871 ms 1.713 ms 1.006 ms
5 ae1.cr1.snjsca11.sonic.net 56.339 ms
...

[klui]

I only request a PD and my router assigns my WAN interface $PD::1/64. That interface is able to ping/traceroute to www.google.com, one.one.one.one.

[daverand]

That's a perfectly legitimate way of operating - but the point is that IA_NA and IA_PD was working. Then it got strange. Then IA_NA stopped working. So, something changed.

[daverand]

Well, everything seems back and stable now:

Jan 10 21:38:01 main10 dhcp6c[70783]: IA_NA address: 2001:5a8:601:22::XXXX pltime=21600 vltime=21600

The IA_NA showed up again, a new IA_PD was offered (boo!), and everything has been stable for 24 hours. Whatever the cause, it seems to have been resolved. Yeah, I wish that the IA_PD was persistent with the DHCP6 DUID, as many of the other carriers do, but I can live with the occasional prefix change.

I know that IPv6 is non-trivial to offer, and to keep running, so I appreciate the fact Sonic is willing and able to do this. As a complete aside, they also started peering this week with one of my other carriers, which has shortened the path between my home and my colo presence. Better connectivity is always a good thing!

Thanks!