What is the subnet mask for the static IP address 10.152.0.4/21?

The IP address 10.152.0.4 with a subnet mask designation of /21 indicates that the first 21 bits are used for the network part of the address. To derive the subnet mask from this CIDR (Classless Inter-Domain Routing) notation, it is useful to convert the prefix length of /21 into its dotted-decimal format.

In binary, a subnet mask for /21 indicates that the first 21 bits are set to '1' and the remaining 11 bits are set to '0'. The binary representation would look like this:

11111111.11111111.11111000.00000000

When you convert each of the blocks of 8 bits into decimal, you get the following:

• The first block (11111111) is 255.

• The second block (11111111) is 255.

• The third block (11111000) is in decimal 248.

• The last block (00000000) is 0.

Combining these gives you the full subnet mask: 255.255.248.0. This means that for any device within this subnet, the network range will include addresses that share the first 21 bits