RBR50 static fixed Ips Comcast

!st off I have had the Obri for four Days or less Love it. I have getting a DOS of service attack on comcastand it seemes many people have had this error but netgear has taken care of it. What I am having a issue with is  I have five fixed Ips ( with Comcast )  and one for router . I was told by Tech Supprt It is not possible to enter the fixed External ips into the ORBI RBR50 ??? Just one. ? Just need to confrim if this is true. Also I have not even been able to get it to except one. Ip any Ideas