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Re: Subneting - Basic Question but doubt full posted 05/19/2006
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HI Alexei,

I am within the subnet boundary. I am only talking about subneting the
192.168.1.0. my first subnet would be /30, second subnet would be /29 third
could be /28, remember its still under the /24 boundary. Why can't I subnet
this IP block like this ?

Frog!
Jumping on the wall



On 5/19/06, Alexei Monastyrnyi <alexeim@xxxxxxxxxxxxxxx> wrote:
>
> No, you cannot do like this.. since /30+/30=/29 you have to assign one
> more /30 network after 192.168.1.0/30 to be able to change from /30 to
> /29 , etc /29+/29=/28..
> i.e. you cannot allocate smaller subnet from  any place of /24 network,
> you have to consider bit boundaries. in your example you cannot allocate
> /27 subnet from 192.168.1.4...
>
> If I am not missing something here.... :-) pls do correct me otherwise
>
> A.
>
>
>
> on 19/05/2006 02:58 Radioactive Frog wrote:
> > Hi Jaiprakash,
> > thanks for answering to my query:
> >
> > Can't we subnet 192.168.1.0 to as below :
> >
> > a) first subnet 192.168.1.0/30 --> valid host 192.168.1.1 to
> > 192.168.1.2broadcast IP
> > 192.168.1.3
> >
> > b) Second subnet 192.168.1.4/27 --> valid host 192.168.1.5 to
> 192.168.1.34 ?
> >
> > and next subnet /28 and next subnet /30 ??????????
> >
> >
> > OR
> >
> > It has to be either 192.168.1.0/26 or /27 or 38, I mean the whole subnet
> > ?????
> >
> > REgards,
> >
> > Frog
> >
> > Ans of 2nd Qusetion ) Subnet mask for  /25 will be 255.255.255.128 (
> Here U
> > can use 2
> >                                  valid Network subnets with 126 valid
> host
> > IPs in each subnet)
> >                                  Subnet mask for /26 will be
> > 255.255.255.192( Here U can use 4
> >                                  valid Network subnets with 62 valid
> > host IPs in each subnet)
> >                                  Subnet mask for /27 will be
> > 255.255.255.224 (Here
> > U can use 8
> >                                  valid Network subnets with 30 valid
> host
> > IPs in each subnet)
> >
> >
> >
> >
> > On 5/19/06, Jai Prakash <jpjsr06@xxxxxxxxx> wrote:
> >
> >> Hi Frog
> >>
> >>   As per my understanding, when u take calss C as a major network and
> >> divides into subnets, it takes all available subnets with valid hosts.
> >>
> >> In your case, if you divide 192.168.1.0/24 into subnets of 30 block
> host
> >> IP.........you will get 8 valid subnet blocks with each having 30 valid
> >> hosts IP. You can use any subnet from these 8 subnets block.
> >>
> >> The theory says.....don't use 1st IP and the Last IP of the subnets
> >> because, they represent Network IP and Broadcast IP accordangliy for
> that
> >> particular subnet.I never seen that books says don't use 1st subnet and
> >> last subnet, when you divide Major Network into subnets.
> >>
> >> The whole discussion outcome is :
> >>
> >> Ans of 1st Qusetion ) U can use 1st and Last subnet of Major Network
> >>
> >> Ans of 2nd Qusetion ) Subnet mask for  /25 will be 255.255.255.128 (
> Here
> >> U can use 2
> >>                                  valid Network subnets with 126 valid
> host
> >> IPs in each subnet)
> >>                                  Subnet mask for /26 will be
> >> 255.255.255.192 ( Here U can use 4
> >>                                  valid Network subnets with 62 valid
> >> host IPs in each subnet)
> >>                                  Subnet mask for /27 will be
> >> 255.255.255.224 (Here U can use 8
> >>                                  valid Network subnets with 30 valid
> host
> >> IPs in each subnet)
> >>
> >> Correct me , if I m wrong................
> >>
> >> Best Regards,
> >> Jai
> >>
> >>
> >>
> >> On 5/18/06, Radioactive Frog <pbhatkoti@xxxxxxxxx> wrote:
> >>
> >>> Hi Guys,
> >>>
> >>> Very basic question but lots of doubt.
> >>>
> >>> 1) First question:
> >>>
> >>> If class C subnet 192.168.1.0 is routed to ISP-B (small) by ISP-A (BIG
> >>> ISP).
> >>> When ISP B starts subneting the 192.168.1.0 IP block for different
> >>> customer
> >>> why do he starts distributing from the first subnet from
> 192.168.1.0/24
> >>> (which sholdn't be used)???????????
> >>> The books and theory says first and last subnet shouldn't be used (as
> >>> network and broadcast subnets), hence we shouldn't use the
> >>> 192.168.1.0/24(first <http://192.168.1.0/24%28first> subnet)
> >>>
> >>> Means the ISP should start distributing from second subnets e.g.
> >>> 192.168.1.32 (see below).
> >>>
> >>> ---------------------------------------------------------
> >>> Subnet          ,   Valid Hosts                       ,   Broadcast
> >>> 192.168.1.0     ,   192.168.1.1 to 192.168.1.30        ,
> 192.168.1.31
> >>> 192.168.1.32    ,   192.168.1.33 to 192.168.1.62      ,   192.168.1.63
> >>> 192.168.1.64    ,   192.168.1.65 to 192.168.1.94      ,   192.168.1.95
> >>> 192.168.1.96    ,   192.168.1.97 to 192.168.1.126     ,
> 192.168.1.127
> >>> 192.168.1.128   ,   192.168.1.129 to 192.168.1.158    ,
> 192.168.1.159
> >>> 192.168.1.160   ,   192.168.1.161 to 192.168.1.190    ,
> 192.168.1.191
> >>> 192.168.1.192   ,   192.168.1.193 to 192.168.1.222    ,
> 192.168.1.223
> >>> 192.168.1.224    ,   192.168.1.225 to 192.168.1.254    ,
> 192.168.1.255
> >>>
> >>>
> >>>
> >>> 1) Second question:
> >>>
> >>> What if ISP starts distributing /25 /26 /27 IP blocks from
> >>> 192.168.1.0/24 IP
> >>> block to the customers ? In this case what subnet mask shouldn't be
> used
> >>> (still first and the last  in 192.168.1.0/24 blocks) ?
> >>>
> >>> Appreciate your answers to this basic topic!
> >>>
> >>> Frog!
> >>>
> >>>
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