What is the first useable host on this subnet?

192.168.1.0 /28

what is the first usable subnet and second useable subnet of this address?

Personally I think the first usable host is 1 on the first subnet and 17 is the first host on the second subnet but for some reason the instuctor at my CCNA class says it is first useable host is 17 and second 33.

I am kind of confused, can anyone help?

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Comments

iproute

ip subnet-zero

remyforbes777

Its obvious they are not using subnet zero. If you are not using subnet zero, you can't have a subnet address of 0.

markzab

ckugelman wrote:

First subnet:
Next subnet: 192.168.1.16

Your instructor isn't accounting for the ip subnet-zero command. Back in the old days, routers didn't have this command enabled and/or didn't support ip subnet-zero. Ip subnet-zero basically just says that you can use the first and the last subnets, where as w/o it, you can't (correct me if I'm wrong, I'm still fairly newbie ).

Edit: Typo!

I agree this is probably what is happening. If you want to like the smart guy go into class tomorrow and tell your instructor that most Cisco routers now have the ip subnet zero command running by default. Therefor the first available subnet would be 192.168.1.0 and the first host 192.168.1.1.

markzab

remyforbes777 wrote:

Its obvious they are not using subnet zero. If you are not using subnet zero, you can't have a subnet address of 0.

At best this is a trick question and he is correct. At worst the instructor is too old school to know about ip subnet zero, and he's still correct.

iproute

ip subnet-zero

mikej412

ckugelman wrote:

Since it's enabled by default since IOS 12 (I think), does the test assume that it's ON (unless otherwise stated) or OFF (unless otherwise stated)?

The CCNA Forum FAQ has the link to this IP Subnet Zero thread.

iproute

mikej412 wrote:

ckugelman wrote:

Since it's enabled by default since IOS 12 (I think), does the test assume that it's ON (unless otherwise stated) or OFF (unless otherwise stated)?

The CCNA Forum FAQ has the link to this IP Subnet Zero thread.

Word.

Kaminsky

ckugelman wrote:

mikej412 wrote:

ckugelman wrote:

Since it's enabled by default since IOS 12 (I think), does the test assume that it's ON (unless otherwise stated) or OFF (unless otherwise stated)?

The CCNA Forum FAQ has the link to this IP Subnet Zero thread.

Word.

Oh yes... been done to death that one.

Nice343 - Your spot on! nice studying

To be able to question a lecturer on subnetting means your learning well.

ckugelman wrote:

... it's enabled by default since IOS 12

Yep. The exams will (ohh they better!!!) tell you about the subnet zero state for the question asked - Verified by at least 1 years worth of forum readers sitting the exam!

Just because a teacher calls himself a teacher doesn't necesarily mean they can teach.
Need to tell your teacher to log onto cisco.com and flash upgrade to Version 12.