There are two similar products; the N600 router and N600 modem router.
The modem router version does support a phone connection to yellow RJ-45 jack.
RJ-11 used to be the rule for phone lines, but often wall sockets are installed as RJ-45 these days.
If your cable is RJ-45 to RJ-45, you should be able to pick up an RJ-45 to RJ-11 adapter from your local electronics store or anywhere that sells fixed phone accessories.