Too many dhcpcd "router available" message in the syslog

Question

I'm visiting my relative's house during this holiday. I bought my Raspberry Pi 3 and other gadgets. The Pi is a media server and a wifi router to share the internet in the guest room.

Everything is working, but I noticed syslog kept recording the following messages in the /var/log/syslog on every few seconds. Following is just an excerpt but the actual number of the records was nearly 100k since the Christmas Eve.

...
Dec 30 20:50:20 RPi-Dev dhcpcd[591]: wlan0: fe80::4270:9ff:fef7:74d7 router available
Dec 30 20:50:23 RPi-Dev dhcpcd[591]: wlan0: fe80::4270:9ff:fef7:74d7 router available
Dec 30 20:50:27 RPi-Dev dhcpcd[591]: wlan0: fe80::4270:9ff:fef7:74d7 router available
Dec 30 20:50:32 RPi-Dev dhcpcd[591]: wlan0: fe80::4270:9ff:fef7:74d7 router available
Dec 30 20:50:41 RPi-Dev dhcpcd[591]: wlan0: fe80::4270:9ff:fef7:74d7 router available
..

I could find a similiar problem here and added a setting that suppresses the message in the /etc/rsyslog.conf as following.

:msg, contains, "router available" ~

Now, rsyslogstopped recording the message. However, I'm not comfortable with it, and I'd like to fix the cause. Could someone explain to me what might be causing it, what I should check and how I can fix it?

Answer 1

Edit /etc/dhcpcd.conf and add a single line to the bottom of the file "noipv6rs" - that does seem to stop the lot by stopping IPV6 route solicitations. I've added nodhcp6 as well to be sure - this alone doesn't stop dhcpcd reporting a friendly, helpful router...