Just my two cents here, there has been a lot of response scattered over all websites' forums about this particular router. (DIR-655 rev B1)
I decided to try and bring this old router to life but it has been very troublesome. I will try to give my advice based on my latest attempt seeming to be the best configuration so far..
My first advice is to accept that trying to configure this old router is like trying to learn advanced skills, so it is probably easier to get a newer router and just go with DD-WRT..(DD-WRT is very tricky to install yourself but works great and can be expensive to find pre-installed)
Okay, I have Comcast 15/2 speed with SB6121 modem and no problems until I switched to this old router..
But, since I want to learn, I have spent so much time tinkering with and will share the results here.
I updated to the latest firmware 2.11NA and have since performed two factory resets since the wireless always seems to start failing. (Apple devices, specifically)
-(All wired devices working great included those hooked to second Netgear router configured as an Access Point.)
SO FAR: Here are my settings in router firmware-
SETUP> INTERNET> click Manual Internet Connection Setup > uncheck "Enable Advanced DNS Service"
SETUP> WIRELESS SETTINGS> click Manual Wireless Connection Setup>
(Okay, here is where I am leaving default settings unchanged to fix MY wireless problem)>
(wireless password was already created from router initial setup,
mixed 802.11n g AND b,
wireless channel will depend on you,
trans. rate "auto",
Ch. width 20 Mhz,
visibility status "visible",
security mode "WPA personal",
WPA mode "WPA Only",
cypher type "TKIP and AES")
Router firmware settings continued-
SETUP> NETWORK SETTINGS> uncheck "Enable DNS Relay"
DHCP reservations (SETUP> NETWORK SETTINGS> DHCP RESERVATIONS LIST) helped connect my old MacBook but not my iPhone 4s iOS 6.1.3 >>> Once I performed another router factory reset and opted not to change the wireless settings, my iPhone and everything seems to connect just fine.
Under ADVANCED> QOS ENGINE> leave Traffic Shaping turned off by default
Under ADVANCED> ADVANCED WIRELESS> I have not changed anything here yet, but I want to disable "WMM" and "short GI" and probably turn down the transmit power (turning WMM "off" is questionable since Apple says just leave it on. https://support.apple.com/en-us/HT202068)
Under ADVANCED> WISH> I do not wish to use Microsoft anymore and don't see any need to enable this (my idea is to turn off most things to make a functional router of this)
Under ADVANCED> turn off WPS (WiFi Protected Setup) will make more secure
So that's it so far, I still need to apply future changes one at a time and wait to see if any issues with wireless. I assume anybody still trying to use this router won't be looking to tap into top speeds so maybe stick with wireless mixed mode 802.11b/g/n even though only have wireless n devices.
I'll admit I like this router, but only if I can get it to work. I much prefer the layout of DD-WRT!
UPDATE: It seems the extra factory resets helped! All wireless connections still good, and I changed each setting one by one until finally I have 802.11n only, with "AUTO: WPA/WPA2 with AES" security. I tried performing a "hard" reset a couple times, so, not sure if it did anything, but it goes a little further than just pressing for ten seconds. Just look up 30-30-30 hard reset method, usually used with 3rd-party custom firmware.