Dhcpv4 and ipv6 dns general page
dhcpv6 setup page indicates it uses dns entry from general setup page entering ivp6 in general dns it trys to enter it into dhcp v4
Feb 23 15:10:28 php: /services_dnsmasq.php: The command '/usr/local/sbin/dhcpd -user dhcpd -group _dhcp -chroot /var/dhcpd -cf /etc/dhcpd.conf -pf /var/run/dhcpd.pid em2' returned exit code '1', the output was 'Internet Systems Consortium DHCP Server 4.2.5-P1 Copyright 2004-2013 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ /etc/dhcpd.conf line 19: semicolon expected. option domain-name-servers 220.127.116.11,18.104.22.168,2620: ^ Configuration file errors encountered – exiting If you did not get this software from ftp.isc.org, please get the latest from ftp.isc.org and install that before requesting help. If you did get this software from ftp.isc.org and have not yet read the README, please read it before requesting help. If you intend to request help from the firstname.lastname@example.org mailing list, please read the section on the README about submitting bug reports and requests for help. Please do not
/var/dhcpd/etc/dhcpd.conf is not DHCPv6 configuration; /var/dhcpd/etc/dhcpdv6.conf is. The problem is with lack of validation on the DHCPv4 part, not the other way round. (Frankly I dislike the entire "heuristics" altogether. Make people specify it explicitely and move on.
there is a hint in dhcpv6 that should be removed
"NOTE: leave blank to use the system default DNS servers - this interface's IP if DNS forwarder is enabled, otherwise the servers configured on the General page."
There is exact same hint in DHCP (v4) page. Again, v4 is supposed to pick up v4 stuff, and v6 is supposed to pick up v6 stuff. What you are seeing is invalid DHCPv4 configuration.