Oi Gilson,
Veja em: http://www.faqs.org/rfcs/rfc950.html
RFC 950 August 1985
Internet Standard Subnetting Procedure
For example, the Internet address might be interpreted as:
<network-number><subnet-number><host-number>
where the <network-number> field is as defined by IP [3], the
<host-number> field is at least 1-bit wide, and the width of the
<subnet-number> field is constant for a given network. No further
structure is required for the <subnet-number> or <host-number>
fields. If the width of the <subnet-number> field is zero, then
the network is not subnetted (i.e., the interpretation of [3] is
used).
For example, on a Class B network with a 6-bit wide subnet field,
an address would be broken down like this:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 0| NETWORK | SUBNET | Host Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Since the bits that identify the subnet are specified by a
bitmask, they need not be adjacent in the address. However, we
recommend that the subnet bits be contiguous and located as the
most significant bits of the local address.
Special Addresses:
From the Assigned Numbers memo [9]:
"In certain contexts, it is useful to have fixed addresses
with functional significance rather than as identifiers of
specific hosts. When such usage is called for, the address
zero is to be interpreted as meaning "this", as in "this
network". The address of all ones are to be interpreted as
meaning "all", as in "all hosts". For example, the address
128.9.255.255 could be interpreted as meaning all hosts on
the network 128.9. Or, the address 0.0.0.37 could be
interpreted as meaning host 37 on this network."
It is useful to preserve and extend the interpretation of these
special addresses in subnetted networks. This means the values
of all zeros and all ones in the subnet field should not be
assigned to actual (physical) subnets.
In the example above, the 6-bit wide subnet field may have
any value except 0 and 63.
RFC 950 August 1985
Internet Standard Subnetting Procedure
Please note that there is no effect or new restriction on the
addresses of hosts on non-subnetted networks.
Grato.
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: "Lista de Discuss�o Rede Wan" <[EMAIL PROTECTED]>
Sent: Tuesday, November 21, 2000 12:30 PM
Subject: [redewan] SubNetting
> Lista de Discuss�o Rede Wan - http://www.networkdesigners.com.br
>
> Colegas:
>
> Conversando com alguns colegas a respeito do uso de sub-redes atrav�s do
uso de
> m�scaras, verifiquei que sempre, � ignorada a primeira e �ltima sub-rede
do
> range das poss�veis.
> Pelas informa��es que obtive, o pessoal justifica este fato que est�
descrito
> em uma RFC.
> A quest�o �: Qual � a RFC onde explica/detalha esta quest�o de n�o se usar
a
> primeira e �ltima sub-redes ??
>
> Me parece que alguns fabricantes de roteadores permitem esta implementa��o
como
> a CISCO onde voc� pode definir um par�metro denominado IP_SUBNET 0.
>
> Algu�m conhece outros fabricantes de routers que permitem esta fun��o ???
>
> Grato pela aten��o,
>
> Gilson Cesar
> Analista de Suporte T�cnico
> HSBC - Bank Brasil S/A.
>
>
>
> -------------------------------------------------------
> Esta mensagem foi enviada usando OndaMail Express.
> http://www.onda.com.br/
> O Onda nao se responsabiliza pelo conteudo deste e-mail
>
>
> ______________________________________________________________________
>
>
|
