Thanks for your kind response, though I don't know much about what you are explaining.
* Robert Elz (k...@munnari.oz.au) wrote: > Just guessing, but this sounds to me like the "prohibiit sending from > tentative addresses" BS that was added a while ago. > > I'd suspect that it goes something like this ... > > host boots, configures itself link-local addresses, and starts DaD > on them - addesses are tentative. > > rtsol (v7) or dhcpcd (v8) starts, and sends a RS to request a > RA from the router. In v7 that is just sent. In v8 it is not, as > DaD isn't finished yet. I previously had rtsol in /etc/ifconfig.wm0 i.e. % cat /etc/ifconfig.wm0 up !rtsol $int But during boot, it complains as rtsol is obsolete, so I remove the second line. So only "up" is still there in the file. Anyway, I saw "Waiting for DAD to complete..." right before router solicitation. So I guess that DAD complete before RS. https://pastebin.com/udwFzp3N > RS's don't get ack'd, the RA is not that, but even if the sender > decides to send another after not seeing a RA fairly soon, it might > still be within the DaD period. > > The v7 host gets the RA, configures global v6 addresses, and all > works, the v8 host does not (quickly). > > Routers send RAs periodically - every 10 minutes is a common config, > so eventually a RA appears, the v8 host configures its v6 addrs (finally) > and all is OK (the actual delay will vary of course, depending upon where > in the router's time sequence of regular RA sending the host boots). Sometimes I have to wait for 30 minutes. > To see if this guess is likely enough to be raised to be a hypothesis, do > two things... > > First, soon after the boot, ping the router's link local address. Since LL > (v6) addresses tend to be obnoxious things, it would be best to have a > script pre-prepared, and tested, for this in advance. Immediately after boot, I can ping6 fe80::1. (I believe it's LL.) > If that works (give it at least a second or two after boot - by the time you > can log in should be OK, but don't automate it in rc.local or anything), and > a ping6 of a global v6 address does not (nb: have the address calculatted > in advance, so it cannot be a DNS issue, and use -n on the pings - always...) > then this is a clue. Right after boot, where ping6 canonical name fails, ping6 global ipv6 address also fails. So it should not be a DNS issue. > Then add > > net.inet6.ip6.dad_count=0 > > to /etc/sysctl.conf and reboot, and try again. If the global v6 ping works > this time, (and the LL ping both times) then this is likely to be the problem. Adding this line to /etc/sysctl.conf and reboot doesn't fix the problem. ping6 LL works but ping6 the public ipv6 address or canonical name doesn't. > On the other hand if a global v6 ping to an address works, and one to a > hostname does not, then that would be evidence of DNS issues, and we > would need to look in a different direction. Both ping6 global address and canonical name fail. > ps: I hope you are on the list, as gmail almost always rejects mail from me. I am on the list. :-) Thank you, -- Gua Chung Lim "UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity." -- Dennis M. Ritchie