Asus RT-N66U, Problem with WiFi DHCP

[Shaun]

I've searched the net and dug into the AsusMerlin Gui for an answer to my problem.
Asus RT-N66U has strange DHCP behaviour for WiFi clients, wired lan connections are OK, and WiFi connected PC's are OK, it just seems like iPhones, USB sticks and Android devices.

Factory default, reload Merlin 380.65, factory default.
Wan is static, lan ip
Lan changed to local lan value 192.168.5.100, dhcp 192.168.5.101, 255.255.255.0
Nothing else changed from default
Extract from system log

Feb 20 08:18:22 dnsmasq-dhcp[235]: DHCPDISCOVER(br0) 04:c2:3e:78:91:5c
Feb 20 08:18:22 dnsmasq-dhcp[235]: DHCPOFFER(br0) 192.168.5.235 04:c2:3e:78:91:5c
Feb 20 08:18:22 dnsmasq-dhcp[235]: DHCPREQUEST(br0) 192.168.1.18 04:c2:3e:78:91:5c <--- WRONG
Feb 20 08:18:22 dnsmasq-dhcp[235]: DHCPNAK(br0) 192.168.1.18 04:c2:3e:78:91:5c wrong server-ID

Looks like the phone is not accepting the DhcpOffer, why not, anyone else seen this behaviour or any ideas.
Had log.dhcp in /jffs/configs/dnsmasq.conf.add script to try and get more info. Can add change dnsmasq values if needed.

Thanks.

 

[ColinTaylor]

Goggling this problem (wrong server-ID) suggests that it's most commonly caused by having more than one DHCP server on the network.