IP subnet zero on new exam

Unanswered Question
Oct 20th, 2007

I'm studying for the new exam and was wondering if IP subnet zero is going to be used on subnetting questions or not. I know in the past if they wanted you to use it the question would indicate that. And why would cisco continue to use the old method when IP subnet zero is used extensively in the real world? Makes no sense at all. Any replies are appreciated, thanks.

I have this problem too.
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motherwolf Mon, 10/22/2007 - 06:58

I think they do need to state it. I've seen numerous pratice questions listing the first available subnet(subnet zero) and the next available subnet(the cisco way)as answers. How would you know to use subnet zero if they didn't state it in the question?

LordFlasheart Mon, 10/22/2007 - 07:42


By default ip subnet-zero is switched on from at least IOS version 12.0 onwards. A lot of practice tests across the web still refer to old strains of the CCNA so that adds to the confusion. I took my exam two years ago and it was all subnet-zero without stating it because it is the Cisco default setting. If it explicitly states not to use subnet zero then don't, otherwise do so.



motherwolf Mon, 10/22/2007 - 08:24

Hey Chris, thanks for the reply. Unfortunately this doesn't really help because you're just another person saying use subnet zero unless the question says not to. I've spoken with people and have read threads in other forums that say the exact opposite. In fact, I'm taking a CCNA class right now and we're being taught not to use subnet zero unless it's specifically stated in the question. Hey here's an idea, does anyone employed by Cisco moderate or browse these forums? If so, how about a concrete answer to this question. Subnet zero, no subnet zero, or the question will simply state what to use? Thanks

LordFlasheart Mon, 10/22/2007 - 11:35

Yes it would be helpful if somebody could set the record straight but if it is any consolation, the latest Cisco Press book for ICND1 has a few practice questions in there and one of them asks how many hosts and subnets does a /28 mask give. The answer is 16 of each so that suggests to me that ip subnet-zero is used and that is what I'm teaching my guys at work.

Personally I don't understand being taught to do something that is not the default behaviour of a Cisco device.....




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