@Brahms as @Virgo pointed out, during your initial setup, which is not that big of a deal since you do it once, set the CPEs to an ip address that makes them accessible from your network.
I am trying to picture your setup. You mentioned you have a CPE510 and a CPE210. I am not quite sure how you are implementing these in your network so a schematic of your layout would really increase your chances of getting the help you need.
Both of the CPE you mentioned are generally for Point to Point (PTP) or Point to Multi Point (PTMP) and are designed to work in pairs, for example one CPE510 aimed at another CPE510. Since the CPE510 and CPE210 cannot connect to each other, since the 510 is 5Ghz and the 210 is 2.4Ghz, it sounds like you are trying to use them as Access Points, which is not an optimal solution.
In image below the upper part is generally how the CPE are configured. The bottom part of the image is a configuration I have used with phenominal resutls. You could do away with the wireless router if you did not need inside wifi at the remote location, and just wire the AP directly to the CPE.
I am not claiming this is your solution. You need to explain your scenario better and what you intend to acheive.