Answer:
255.255.255.0
Step-by-step explanation:
Given data
base IP address = 198.10.0.0/20
receives addressed = 198.10.10.144
to find out
network mask used by the router
solution
we know mask is combination of 32 bit used
describe to portion in addressed refers to subnet that is
we know IP address = 198.10.0.0/20
here a = 198, b = 10 and c = 0 and d = 0 and n = 20
so it will be 20 bits + 12 bits
20 bits are 1 1 1 1 1 1 1 1 . 1 1 1 1 1 1 1 1. 1 1 1 1 1 1 1 1
12 bits are 0000.0000.0000
so default natural mask are
Class A is 255.0.0.0
Class B is 255.255.0.0
Class C is 255.255.255.0