Class Inter-Domain Routing (CIDR)

Question 1

/25

Answer 1

■ 128 mask
■ 1 bit on and 7 bits off (10000000)
■ Block size of 128
■ 2 subnets, each with 126 usable hosts

Question 2

/26

Answer 2

■ 192 mask
■ 2 bits on and 6 bits off (11000000)
■ Block size of 64
■ 4 subnets, each with 62 usable hosts

Question 3

/27

Answer 3

■ 224 mask
■ 3 bits on and 5 bits off (11100000)
■ Block size of 32
■ 8 subnets, each with 30 usable hosts

Question 4

/28

Answer 4

■ 240 mask
■ 4 bits on and 4 bits off (11110000)
■ Block size of 16
■ 16 subnets, each with 14 usable hosts

Question 5

/29

Answer 5

■ 248 mask
■ 5 bits on and 3 bits off (11111000)
■ Block size of 8
■ 32 subnets, each with 6 usable hosts

Question 6

/30

Answer 6

■ 252 mask
■ 6 bits on and 2 bits off (11111100)
■ Block size of 4
■ 64 subnets, each with usable 2 hosts

Question 7

/31

Answer 7

■ 254 mask
■ 7 bits on and 1 bits off (11111110)
■ Block size of 2
■ 128 subnets, each with 1 host.

Cisco (point to point)
Used on Serial and Ethernet interfaces (ISP)