What is Subnet Mask for the 255.255.255.248?

Answer: The address 255.255.255.248 is itself a subnet mask for the /29 CIDR address.

The 255.255.255.248 has no subnet mask as it itself is a subnet mask. It can be subnet mask of Class A, Class B or Class C address. In CIDR representation it is the subnet mask of /29 networks.

Below table represents the number of network, subnets and hosts in different Class of IP where 255.255.255.248 is subnet mask.

Class of IP	No of Networks + Subnet bits	Number of Subnets	Number of Hosts
Class A	8 + 21	221 – 2 = 2097150	23 – 2 = 6
Class B	16 + 13	213 – 2 = 8190	23 – 2 = 6
Class C	24 + 5	25 – 2 = 30	23 – 2 = 6

Conclusion

The subnet mask 255.255.255.248 is equivalent to /29 in CIDR notation. In binary, it looks like this: 11111111.11111111.11111111.11111000. This means that there are 29 bits set to 1 in the subnet mask, leaving 3 bits for host addresses.

With a subnet mask of 255.255.255.248 (/29), you can have a total of 8 IP addresses in the subnet, with 6 addresses available for hosts, since 2 addresses are reserved for network address and broadcast address.

So, in conclusion, for the subnet 255.255.255.248:

Network address: X.X.X.0
First usable IP address: X.X.X.1
Last usable IP address: X.X.X.6
Broadcast address: X.X.X.7