I want to assign our domain name to the static ip... but I cant make out what is my static ip? when I try what is my ip I get XXX.XXX.62.227... but when I asked my service provider they said the the ip range allocated to us was XXX.XXX.51.80/29. How can I find out what is my static ip?
That "/29" defines a subnet, a range of addresses. They could be dynamically assigned, or they could be a range of static addresses that have been provided to you to use as you wish. A subnet that small only provides for 6 IP Addresses (well... 8, but two are used for network administration and should not be assigned to a device). basically, 81 through 86 for the last number (called an octet) in the IP Address.
The fact that our tool finds a different third octet concerns me, however. It seems like you're using Network Address Translation (NAT) somewhere. Try this from a command line on one of your computers:
When you hit ENTER, you'll get a series of lines with time results and (hopefully) various IP Addresses. See what the first two or three "hops" (as they are called) give you for addresses.