First of all, I don't have a modem but instead a FIOS router which, if I use as a primary router, passes the test.  It is impossible to connect my computer to ethernet ONT without a router.
All the other routers I have tested (Netgear, Linksys, Buffalo, FIOS Actiontec) all pass the test as stealthed, so providing this feature is RUDIMENTARY and BASIC.
Indeed, the previous versions of DIR-655, as I understand from other posters, PASS this test, so there is no reason why REV B1 should NOT pass.  D-Link can certainly get the job done if they want to....EASILY.
One of the primary reasons for using a router is as a first defense firewall device.  If it cannot provide a basic feature, then I must wonder about D-Link as a reputable router manufacturer.
I have a case open with tech support.  Their initial reaction has been one of DENIAL.  That it SHOULD pass and I am not doing something right.  They will test at their end and get back to me.