Classless In - addr .arpa Reverse Lookup Zone

Hi,

I need some help to create a reverse look up zone on the Peplink.

suppose that an ISP has given the address range 109.162.160.201 - 109.162.160.206 with subnet ID 109.162.160.200 and broadcast address 109.162.160.207 with a subnet mask of 255.255.255.248 to a company with the DNS name netssa.net.

how can I create a reverse look-up zone and PTR for my mail server reverse look-up with address mail.netssa.net and IP address of 109.162.160.203 ?

Thank you so much.