ip subnet zero

The Cisco Press book mentions to avoid the zero and broadcast subnet if:

Classful routing protocol
Rip Version 1 or IGRP as routing protocol

Is this saying that if the protocol is classful, rip v1 or IGRP and it does not mention ip subnet zero is enabled, then one should assume that the zero and broadcast subnets will not be used?

Is this literally applicable to the exam?

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Comments

spd3432

RIPv1 and IGRP are both classful routing protocols. There is no subnet information passed with routing table updates. Therefore, there is no subnet 0 since an entire network (A, B, or C) is used.

lon21

Sorry I don't undertstand what ip subnet-zero is used for?

I'm correct in saying that when this cmd is enabled the router can accept the subnet as a 0 and the broadcast as a 0 aswell?

Thanks

jwashington1981

lon21 wrote: »

Sorry I don't undertstand what ip subnet-zero is used for?

I'm correct in saying that when this cmd is enabled the router can accept the subnet as a 0 and the broadcast as a 0 aswell?

Thanks

ip subnet zero allows you to use the first and last subnets in a network. When you calculate your subnets, you would always have to subtract two subnets. This command allows you to use all subnets.