I set up a new router here with recent LEDE and everything works as expected.
Only some warnings in the logs are annoying me. Mostly because I can't figure out
what they are about.
The log reads
Mon Nov 6 12:14:22 2017 daemon.warn odhcpd[11272]: DHCPV6 SOLICIT IA_NA from 00030001f0795937acd0 on br-lan: ok fda3:6e4d:4b92:10::29e/128
Mon Nov 6 12:16:17 2017 daemon.warn odhcpd[11272]: DHCPV6 SOLICIT IA_NA from 00030001f0795937acd0 on br-lan: ok fda3:6e4d:4b92:10::29e/128
Mon Nov 6 12:18:14 2017 daemon.warn odhcpd[11272]: DHCPV6 SOLICIT IA_NA from 00030001f0795937acd0 on br-lan: ok fda3:6e4d:4b92:10::29e/128
Yes, and you can get rid of it; but you said it's not an option...you need to disable DHCPv6 and RA on your LAN. Specifically RA.
Yes, and it's also noted in an old bug report flagged as 'worksforme,' which is why you find that exact information on the Wiki: https://dev.openwrt.org/ticket/17715
The clients on your LAN are seeking IPv6 servers, IPs, etc. You could disable their IPv6 instead.
loglevel is bit mask and consists of bits, each of them enable specific messages like error, warning, debug
dont remeber exactly. 4 means error only, 0 means nothing
The problem was a computer with an integrated ASMB8-iKVM management console. Even with recent firmware it was not able to issue a correct DHCPv6 request. Therefore the solution was to disable IPv6 on the client.
You actually can set the loglevel of odhcpd to something lower than 4 (warning) to suppress the warning messeages and everything above. You are just missing the option in your config file: