My specific settings on the router:

Router: Buffalo WHR-HP-AG108
Firmware: DD-WRT v24-sp2 (10/10/09) std - build 13064

This router has 2 network interfaces (one is A, one is B/G). I will skip listing the settings for the A interface since N900 does not have 802.11a and is irrelevant here.

The second interface is the B/G antenna and here are my settings:

Regulatory Domain - UNITED_STATES
TX Power - 20 dBm
Antenna Gain - 0 dBi
Wireless Mode - AP
Wireless Network Mode - Mixed
Noise Immunity - Auto
Noise Immunity Level - 4
OFDM Weak Detection - Enable
Protection Mode - None
RTS Threshold - Disable
Transmission Minimum Rate - Auto
Transmission Maximum Rate - Auto
Short Preamble - Disable
Extended Range - Disable
Super G Fast Framing - Disable
Outdoor Band - Disable
Channel Width - Full (20 MHz)
Diversity - Disable
TX Antenna - Primary
RX Antenna - Primary
AP Isolation - Disable
WMM Support - Disable
Wireless Network Name (SSID) - whatever
Radar Detection - Disable
Wireless Channel - Auto
Wireless SSID Broadcast - Enable
ScanList - default
Sensitivity Range (ACK Timing) - 2000
Max Associated Clients - 256
MTik Compatibility - Disable
Network Configuration - Bridged



In the Wireless Security section, this interface is set up as:
Security Mode - WPA2-Personal
WPA Algorithms - AES
WPA Shared Key - secret
Key Renewal Interval (in seconds) - 3600


WDS is disabled. MAC filter is disabled.

I am using DNSMasq (enabled on Services page) and on the main Setup page I have "Use DNSMasq for DHCP", "Use DNSMasq for DNS" and "DHCP-Authoritative" all enabled.

Hope that helps.