From: Godswill Oletu (oletu@inbox.lv)
Date: Thu May 18 2006 - 23:08:13 ART
Radioactive,
You can use any subnet you wish so long, you are not over lapping each
address space and also obeying all the underlying rules. Enabling subnet
zero, will allow you to use the zero subnets.
It is possible to use the /30 addresses you indicated in your previous post
ie 192.168.1.0/30 (192.168.1.1 & 192.168.1.2 are valid hosts # 192.168.1.3
as the broadcast).
But you would not be able to use the /27 addresses you indicated in your
post because, those address space will overlap with address spaces from /30
example.
To understand this, eg if you start with eg the /30 address space your
networks will be 192.168.1.0; 192.168.1.4; 192.168.1.8; 192.168.1.12;
192.168.1.16; 192.168.1.16;.....keep increasing by the value of 4 and you
can subnet the whole class C with /30. But if you want to start subnetting
the same class with /27 at one point, you have to wait for the proper bit
boundary, eg /27 means 32 hosts (30 valid hosts), you should know how to do
that maths by now.
For you to start addressing with the /27 subnets, wait for a corresponding
bit level on the /30 address space, you see that an address of
192.168.1.0/27 will not be valid because it will overlap with
192.168.1.0/30; Your earliest opportunity to start the /27 addressing will
start after 192.168.1.28/30 subnet, so instead of making the next subnet
192.168.1.32/30, go ahead and make it 192.168.1.32/27; the next subnet will
then be 192.168.1.64/27; 192.168.1.96/27, etc. etc...
If see that, you can start and stop subnetting at any bit boundary you want,
however in order not to wast addresses unnecessary, one have to carefully
plane this ahead of time.
HTH
Godswill Oletu
----- Original Message -----
From: "Radioactive Frog" <pbhatkoti@gmail.com>
To: "Jai Prakash" <jpjsr06@gmail.com>
Cc: <ccielab@groupstudy.com>
Sent: Thursday, May 18, 2006 8:58 PM
Subject: Re: Subneting - Basic Question but doubt full
> 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@gmail.com> 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@gmail.com> 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!
> > >
> > >
This archive was generated by hypermail 2.1.4 : Thu Jun 01 2006 - 06:33:21 ART