From: Alexei Monastyrnyi (alexeim@orcsoftware.com)
Date: Fri May 19 2006 - 07:48:03 ART
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@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!
>>>
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>
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