[CentOS] systemd automount of cifs share hangs

[Kenneth Porter]

On 10/26/2018 12:25 PM, mark wrote:
> Wait a minute: are you running IPv6? What we see is that if a system
> doesn't get its IPv6 address, NFSv4 goes preferentially for that, and if
> it has that, and looses it, it will*NOT*  fall back to IPv4, but hangs.

All my interfaces have a link local IPv6 address.

Note that only the automount hangs. The regular mount unit works fine. 
It also seems that once the mount is manually mounted and allowed to 
expire, it automounts again just fine. (I have the TimeoutIdleSec set to 
10 for testing.) It's a production server so I can't easily reboot it to 
test the failure. I reboot it about once a month when a new kernel comes 
out.