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martin
Guest
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 Posted: Sat Aug 09, 2003 7:41 am Post subject: Calculating hosts in a Subnet: CONTRADICTION - Help please!! |
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Wendell Odom (In CCNA Certification guide 640-507) states:
" The number of subnets per network is defined by this formula:
2 ^ number of subnet bits
In some documents the number of subnets is shown as 2 less than 2^ number of
subnet bits, implying two reserved cases. These two cases are no longer
reserverd, however and can be used."
Tod Lammle (In CCNA Study Guide 3rd Edition 640-607) states:
" How many subnets ? 2 ^x - 2 = number of subnets. x is the number of masked
bits. "
So my quesiton is:
Which is correct FOR THE PURPOSES OF THE EXAM ???
Thanks,
Martin. |
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Ryan Goolevitch
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| Posted: Sat Aug 09, 2003 8:01 am Post subject: Re: Calculating hosts in a Subnet: CONTRADICTION - Help plea |
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sure 2 ^ 2 would be 16 raw IP address in that subnet. However, the first is
always the network address, and the last is always the broadcast address.
leaving you 2 less you can actually use for hosts.
Ryan
"martin" <bajelisNO@SPAM4MEozemail.com.au> wrote in message
news:3f345f41$0$23595$5a62ac22@freenews.iinet.net.au...
| Quote: |
Wendell Odom (In CCNA Certification guide 640-507) states:
" The number of subnets per network is defined by this formula:
2 ^ number of subnet bits
In some documents the number of subnets is shown as 2 less than 2^ number
of
subnet bits, implying two reserved cases. These two cases are no longer
reserverd, however and can be used."
Tod Lammle (In CCNA Study Guide 3rd Edition 640-607) states:
" How many subnets ? 2 ^x - 2 = number of subnets. x is the number of
masked
bits. "
So my quesiton is:
Which is correct FOR THE PURPOSES OF THE EXAM ???
Thanks,
Martin.
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Sebek
Guest
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| Posted: Sat Aug 09, 2003 6:31 pm Post subject: Re: Calculating hosts in a Subnet: CONTRADICTION - Help plea |
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U¿ytkownik "Mark Bedingfield" <atari030@optusnet.nomorespamta.com.au>
napisa³ w wiadomo¶ci news:3f346f8e$0$28120$afc38c87@news.optusnet.com.au...
| Quote: | The number of subnets is 2n-2 for the purposes of the Exam. But the RFC
says
2n. Cisco believe otherwise. So always use 2n - 2 for subs.
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But if you use command ip subnet-zero in Cisco router you are able to use
zero subnet also. But genarally during CCNA exam the correct answer is 2n-2
subnets. |
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André Franke
Guest
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| Posted: Wed Aug 13, 2003 7:12 pm Post subject: Re: Calculating hosts in a Subnet: CONTRADICTION - Help plea |
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| Quote: | You can enable usage of the zero-subnet/host and the
broadcast-subnet/host
by issuing the "ip subnet zero" command, but by default it is set to "no
ip subnet zero". So unless explicitly enabled it will exclude the
subnetaddress and the broadcastaddress for every subnet. Thus default is
2^n-2.
regards
André
Got to correct this. According to Cisco in most current IOS versions "ip |
subnet zero" is enabled by default. However, within exams they still
assume it is disabled and you have to do the 2^n-2 unless they say subnet
zero is used too.
regards
André |
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