請問各位這條答案為何會是c?

[mok2000]

請問各位這條答案為何會是c?????????

4. Your network uses an address of 172.30.0.0/16. Your initially will need 25 subnets
with a minimum of 1,000 hosts per subnet.. The projected growth for next year
though, indicates a need for at least 55 subnets. What subnet mask should you configure to
meet these needs?

A. 255.255.240.0
B. 255.255.248.0
C. 255.255.252.0
D. 255.255.254.0
E. 255.255.255.0


Answer: C

[tahoo]

最初由 mok2000 發表
請問各位這條答案為何會是c?????????

4. Your network uses an address of 172.30.0.0/16. Your initially will need 25 subnets
with a minimum of 1,000 hosts per subnet.. The projected growth for next year
though, indicates a need for at least 55 subnets. What subnet mask should you configure to
meet these needs?

A. 255.255.240.0
B. 255.255.248.0
C. 255.255.252.0
D. 255.255.254.0
E. 255.255.255.0


Answer: C

因為子遮罩為255.255.252.0 表示要切64個subnets太多,題目只要25個,所以只要切成255.255.248.0切成32個subnets,每一段有8*255個ip,所以一定夠題目的最少1000台
但是最後題目又要達到最少55個網段,選b才32個,選c會有64個,所以只好選c才對

[alphaone]

你可以這樣想比較快
至少一千台，所以至少需要四個c class subnet。那麼往回推一層四個subnet要怎麼切呢？256-4=252，所以答案是255.255.252.0。

[scarf]

是這樣子的喔 這樣的講解真是詳細耶~

[mok2000]

多謝大家指點