Is subnetting works for public IP addresses also

[radhakrishnan.mathiyalagan]

In our DC we have ASA 5525 Firewall, while logging into ASDM and under the routes tab i have seen directly connected network 115.110.162.144 255.255.255 so there are 8 IPs starting from 115.110.162.144 to 115.110.162.151, This is Public IP addresses so I want to understand whether the first public IP 115.110.162.144 is reserved as Network address and last public ip 115.110.162.151 is reserved as broadcast address and we can assign public IPs from 115.110.162.145 to 115.110.162.150 to the router and firewall interfaces????

Kindly help me understand whether subnetting works for Public ip addresses also, if so First and last IPs are reserved or not??

If we require one public IP for our internet gateway, whether we need to purchase 3IPs from IANA(1 for Network Address, 1 for assigning WAN interface of router and 1 for broadcast address??

[Kasun Bandara]

you can assign public IPs from 115.110.162.145 to 115.110.162.150 . normally IP addresses are provided by IANA is /24 subnets. they are purchased by ISPs and assigning smaller subnets to clients. you can request different subnet sizes from ISP as per your requirement. also if you are planning to get IP block from IANA, you need to provide reasons for the requirement and few more details to get approval form them.   

for ILL like connections, we need to avoid using network and broadcast addresses. but for connections like dialup, you will get single IP most of the times.

[Richard Burts]

There are aspects of the original post that I do not understand. For example "i have seen directly connected network 115.110.162.144 255.255.255". How does this indicate a block of 8 addresses? That address could just as easily be the beginning of an block of 16 addresses (or of 4 addresses).

But getting beyond that confusion is a valid question of whether the ASA needs to reserve the beginning and ending addresses of the block (the network address and the broadcast address). I believe that the answer depends on how the ASA will use the address block. If the ASA is going to assign an IP address in the block to an interface, then the rules about reserving the first and last address do apply. If the ASA is going to use the addresses simply for Address Translation then there is no need to reserve first and last address.