Landline connection to AX6 CAX30

What actual model do you have? AX2700 is a speed. 

If you're referring to the CAX30, no, it does't have voice capability. 

You could always get some type of voip service/device like Ooma. 

The CAX30 doesn't support VOIP phone services.   I had VOIP phone service with AT&T and the AT&T modem - router had a phone jack to plug in your phone.  When I moved to Xfinity I bought the same router - modem as you the CAX30; it has no jack to plug your phone into.  I solved the problem by buying a Ooma device that connects to one of the four ethernet ports on the back of the CAX30. You then have to plug your phone into the Ooma device.   You can buy the Ooma device from Ooma or Best Buy for around $70.   The Ooma service is free but you have to pay for local charges and taxes which comes to around $7.25 a month where I live.  On initial setup you have to choose a new telephone number from a list of available numbers in your area.  If you want to keep your old number you can request to have it ported over to Ooma for a $40 charge.  Don't cancel your old phone service before porting over your old number or you will lose it.