I have a netgear router attached to my gateway (going on 5 years now). About a year ago, I noticed a slow down with Internet speed. Google.com pings would range 500-700ms wher eit is normally 35-50ms. I took the Netgear out of the DMZplus mode (set it to maximum protection mode) and rebooted the gateway and the netgear. Problem went away. Now, any time I place the Netgear in the DMZplus mode, the high pings eventually return, not immediately, but usually within a few hours. My Netgear has an IP of 192.168.2.1. Any ideas on why this might be happening? Note: I have wirless disabled on Gateway so no interference there. This problem occurs wireless or wired.
Obviously something going wrong with the NetGear router, maybe a hardware issue. Could be a power supply or capacitor that's going bad, especially after 5 years. Could also be a heat-related issue since you say it will work decent for a while but starts acting up after a few hours.