said by NetFixer:said by rendrenner:You don't by chance have phone service do you? Its not that uncommon for homes to have their own modem for CHSI and Comcast modem for voice.
Except that neither the CM820A or the SB6121 are EMTAs.
Of course SB modem isn't, that's why it would have been the CHSI only modem on a dual modem setup.
My error on the part of misreading the 820 as an 802