Answer:
The subnet mask for all networks in the site is = 255.255.255.224
Explanation:
IP version 4 addresses have three main classes, they are;
Class A : 0 - 126
Class B : 128 - 191
Class C : 192 - 223
And they are define in terms of host and network portion, by the subnet mask.
Class A: 10.0.0.0 , subnet mask: 255.0.0.0
Class B: 172.16.5.3 , subnet mask: 255.255.0.0
Class C: 192.168.2.4 , subnet mask: 255.255.255.0
The "255" on the mask represents the network portion on the ip address, while "0" represents the host.
IPv4 addresses are 32 bits, with each for the four portions are 8 bits (or octet).
The highest number of host is; IP phones = 22 addresses
To get the mask, we have to get the number of possible host;
host= 2
To get a little close to 22, we substitute 5;
=2
=32 - 2 = 30 hosts
subnet mask; 255 . 255 . 255 . 255
11111111 11111111 11111111 1 1 1 00000
the 1s at the left of the last octet;
=2 + 2
+ 2
= 128 + 64 + 32 = 224
The subnet mask for the site is = 255.255.255.224