RT-n66u errors in syslog

[dikkiedirk]

I currently run the 420 firmware and see these lines in the syslog:

Nov 14 17:07:50 dnsmasq-dhcp[504]: DHCPACK(br0) 192.168.10.248 00:09:b0:41:4a:00
Nov 14 17:07:58 dnsmasq-dhcp[504]: DHCPDISCOVER(br0) 192.168.100.12 00:09:b0:41:4a:00
Nov 14 17:07:58 dnsmasq-dhcp[504]: DHCPOFFER(br0) 192.168.10.248 00:09:b0:41:4a:00
Nov 14 17:07:58 dnsmasq-dhcp[504]: DHCPREQUEST(br0) 192.168.10.248 00:09:b0:41:4a:00

repeating very often.

What is wrong here? How to get rid of this?
The speed when downloading drops significantly and the router seems to restart after a while. download speed is great then. Should I set a static IP?