subnet-zero when to configure

subnet-zero configuration

ip subnet-zero. what is the purpose of this cisco command? When and where to use this command?

ip subnet-zero What this command does? Suppose you have 256 public ip addresses (213.5.5.0/24) under your control. You have 4 branch offices and each branch needs 64 ip addresses. You will split the 256 ip like this: 213.5.5.0 to 63 ... first subnet 213.5.5.64 to 127 ..second subnet 213.5.5.128 to 191..third subnet 213.5.5.192 to 255 ...last subnet

As per the old subnetting rules, you cannot use the 1st subnet 213.5.5.0-63 as well as last subnet 213.5.5.192-255. But this first and last subnet can be used, if you configure the command: “ip subnet-zero”.

Whereever possible, don’t use this zero subnet. Because, the old protocols such as RIP and IGRP cannot handle zero-subnet. When using these protocols, configure “no ip subnet-zero”

So, the meaning of “ip subnet-zero” is “Routerji ! Forgive me. I cant afford to waste so much of ip addresses just because of some old junk rules. Please allow me to use these ALL ZERO AS WELL AS ALL ONES subnets. Thank you ”

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