first, class-full routing, and description of address space, is ancient
history. in particular, many DSL providers are being assigned slices
of what used to be called a class A address, and individual customers
of those providers get subsets (smaller contiguous non-overlapping
ranges) of those "slices." so a DSL subscriber is unlikely to get a
address range with a 24 bit network mask (the equivalent of the old
class C network description); one is more likely to get something like
a /29 (leaving 3 bits for the customer, the provider's router interface,
etc.).
if you are running a firewall or other device that does address
translation, then you can use any address space you want behind
it, with whatever network mask you like.
-paul
--On Wednesday, 23 February, 2000 08:46 -0800 Steven Pierce
<[EMAIL PROTECTED]> wrote:
> Mark,
>
> Thank you very much more this wonderful information. Question... If I
> have a class "C" then anything I use behind the firewall can be assigned
> a 192 address? That way I am not using all my IP address for internal
> networks. I have a DSL line at home and getting ready to setup a
> hosting service. Small, just a few to start.
>
> Thank you again.
>
> Steven
>
> *********** REPLY SEPARATOR ***********
>
> On 2/23/2000 at 5:29 AM [EMAIL PROTECTED] wrote:
>
>> IP Addressing
>> IP address descriptions are found in RFC 1166, Internet Numbers. The
>> Internet Network Information Center (InterNIC) maintains and
>> distributes the RFC documents. The InterNIC also assigns IP addresses
>> and network numbers to Internet Service Providers (ISPs), who in turn
>> provide to their customers a range of addresses appropriate to the
>> number of host devices on their network.
>> The section that follows describe the various types of IP addresses,
>> how addresses are given, and routing issues related to IP.
>> IP addresses are written in dotted decimal notation consisting of four
>> numbers separated by dots (periods). Each number, written in decimal,
>> represents an 8-bit octet (sometimes informally referred to as a byte)
>> giving each number a range of 0 through 255, inclusive. When strung
>> together, the four octets for the 32-bit IP address.
>> IP Address Notation
>>
>> 32-Bit Value
>> Dotted Decimal Notation
>> 01100100.01100100.01100100.00001010
>> 100.100.100.10
>> 11000011.00100000.00000100.11001000
>> 195.32.4.200
>> The largest possible value of a field in dotted decimal notation is
>> 255, which represents an octet where all the bits are 1s.
>> IP Address Classes
>> IP addresses are generally divided into different classes of addresses
>> based on the number of hosts and subnetworks required supporting the
>> hosts. As described in RFC 1166, IP addresses are 32-bit quantities
>> divided into five classes. Each class has a different number of bits
>> allocated to the network and host portions of the address.
>> For example, 192.168.45.x describe a Class 'C' network with addresses
>> ranging from 192.168.45.0 through 192.168.168.255.
>> Class 'A' Addresses
>> The class 'A' IP address format allocates the highest 8 bits to the
>> network field and sets the highest-priority bit to 0(zero). The
>> remaining 24 bits form the host field. Only 126 class 'A' networks
>> can exist (0 is reserved and 127 is used for loopback networks), but
>> each class 'A' network can have almost 17 million hosts. No new class
>> 'A' network can be assigned at this time.
>> Class 'B' Addresses
>> The class 'B' IP address format allocates the highest 16 bits to the
>> network field and sets the two highest-order bits to 1 and 0, providing
>> a range from 128 through 191, inclusive. The remaining 16 bits
>> providing a range from 128 to 191, inclusive. The remaining 16 bits
>> form the host field. More than 16,000 class 'B' networks can exist,
>> and each class 'B' network can have up to 65,534 hosts.
>> Class 'C' Addresses
>> The class 'C' IP address format allocates the highest 24 bits to the
>> network field and sets the three highest-order bits to 1,1, and 0,
>> providing a range from 192 through 223, inclusive. The remaining 8
>> bits form the host field. More than two million class 'C' networks
>> can exist, and each class 'C' network can have up to 254 hosts.
>> Class 'D' Addresses
>> The class 'D' IP address format was designed for multicast groups, as
>> discussed in RFC 988. In class 'D' addresses, the 4 highest-order bits
>> are set 1, 1, 1, and 0, providing a range from 224 through 239,
>> inclusive. Class 'D' addresses is currently used primarily for the
>> multicast backbone (MBONE) of the Internet. Many routers and
>> firewalls do not support MBONE or multicast and therefore ignore class
>> 'D' addresses.
>> Class 'E' Addresses
>> The Class 'E' IP address is reserved for future use. In Class 'E'
>> addresses, the 4 highest-order bits are set to 1, 1, 1, and 1. Routers
>> and Firewalls currently ignore class 'E' IP addresses.
>> Reserved IP Addresses
>> Some IP addresses are reserved for special uses and cannot be used for
>> host addresses. The following table lists ranges of IP addresses and
>> shows which addresses are reserved, which are available to be assigned
>> and which are for broadcast.
>> Class
>> IP Address
>> Status
>> A
>> 0.0.0.0
>> Reserved
>>
>> 1.0.0.0 through 126.0.0.0
>> Available
>>
>> 127.0.0.0
>> Loopback networks on the local host
>> B
>> 128.0.0.0
>> Reserved
>>
>> 128.1.0.0 through 191.254.255.255
>> Available
>>
>> 191.255.0.0
>> Reserved
>> C
>> 192.0.0.0
>> Reserved
>>
>> 192.0.1.0 through 223.255.254.255
>> Available
>>
>> 223.255.255.0
>> Reserved
>> D
>> 224.0.0.0 through 239.255.255.255
>> Multicast group addresses
>> E
>> 240.0.0.0 through 255.255.255.254
>> Reserved
>>
>> 255.255.255.255
>> Broadcast
>> Private IP Networks
>> RFC 1918 reserved three IP network addresses for private networks. The
>> addresses 10.0.0.0/8, 192.168.0.0/16 and 172.16.0.0/20 can be used for
>> anyone for setting up their own internal IP networks.
>>
>>
>>
>>
>> Johann van Duyn <[EMAIL PROTECTED]>
>> Sent by: [EMAIL PROTECTED]
>> 02/23/00 04:36 AM
>>
>>
>> To: [EMAIL PROTECTED]
>> cc:
>> Subject: Private IP address ranges?
>>
>>
>>
>>
>> Hi...
>>
>> I am planning on using NAT on my firewall, and need to know what IP
>> address ranges are safe to use on my internal network, so as not to
>> have addresses on my internal network that are the same as those of
>> actual sites on the Internet. Could anyone please either tell me what
>> the correct ranges would be for class A, B and C, or point me to a
>> resource where I could find that info?
>>
>> Thanks
>>
>> Johann van Duyn
>>
>> ***The Appleton Group Ltd***
-
[To unsubscribe, send mail to [EMAIL PROTECTED] with
"unsubscribe firewalls" in the body of the message.]
