CM700 gigabit ethernet port will only connect at 100MBps

I recently upgraded my Comcast service to Blast Pro (200Mbps) and purchased a CM700 modem to enable me to take advantage of it.  However I've run into a serious obstacle: the (gigabit) ethernet port on the CM700 will only connect at 100 Mbps, preventing me from taking full advantage of available bandwidth.  I have tried a half dozen known good cat5e/6 cables, connecting the modem to a gig switch (instead of router), connecting with laptop, always 100 mbps link.

This afternoon I called comcast to see if it was related to provisioning on their end, they assured me that I was set up for 200Mbps.  Speed test shows about 95Mbps (saturating 100Mbps connection).  I asked about firmware upgrades and they told me "we don't touch customer owned modems, we won't upgrade the firmware) but I know that to be false based on previous experience with prior modem.  Not sure if it's relevant, but the admin interface shows that I have firmare version v1.01.09, and according to this page:

https://netgear-us.custhelp.com/app/answers/detail/a_id/25477/~/current-firmware-version-for-netgear-cable-modem-routers

most recent firmware comcast firmware version for CM700 is v1.01.05.

Anyone have any suggestions?  About to return this thing and swear off netgear products forever.