Modem ethernet cable light flashing amber

netgear modem:  model CM400

TP-Link router:  450Mbps Wireless N Router

service Comcast

internet is functional (wifi and wired through router)

all lights other than modem ethernet cable light show solid green

when directly connecting modem to computer no internet service, unknown network.

when connecting directly through router cable ports, service near suppposed service speeds.

both my modem and router are rated for speeds far surpassing my service speed.

Why is the modem's ethernet cable light flashing amber?

What does this indicator mean?

Does this have an impact on my wifi/wired internet speed?

How can I resolve this flashing light?