IP addresses

I'm a newbie who is trying to teach myself a bit more about how things work
on the net, and I have struck a dilemma. Below I will write how I believe IP
addresses work (from what I've read). Please point out where my logic and /
or assumptions have broken down. I'm sure some of you will have fun laughing
at me, but here goes

Every computer must have an IP address to connect to the internet. No two
computers can hav the same address. When you log on to the net through an
ISP, each router you log on throgh has it's own address, and your computer
actually uses that IP address for that session (server assigned IP
addresses). But then I realize that my router has its' own address, and it
is static. I can only assume that every router of that model has the same
address, as it it given in the manual. That flies in the face of my belief
that no 2 machines can have the same IP address. What huge hole in the
fabric of my knowledge did I just fall through?
Johnno.
Replace "invalid" with ".com.au" to reply.




Johnno

Johnno wrote:
> I'm a newbie who is trying to teach myself a bit more about how
> things work on the net, and I have struck a dilemma. Below I will
> write how I believe IP addresses work (from what I've read). Please
> point out where my logic and / or assumptions have broken down. I'm
> sure some of you will have fun laughing at me, but here goes
>
> Every computer must have an IP address to connect to the internet.
> No two computers can hav the same address. When you log on to the
> net through an ISP, each router you log on throgh has it's own
> address, and your computer actually uses that IP address for that
> session (server assigned IP addresses). But then I realize that my
> router has its' own address, and it is static. I can only assume
> that every router of that model has the same address, as it it
> given in the manual. That flies in the face of my belief that no 2
> machines can have the same IP address. What huge hole in the fabric
> of my knowledge did I just fall through?
> Johnno.
> Replace "invalid" with ".com.au" to reply.

Because you are in Australia everything is upside down.

;-)

--


Travis in Shoreline Washington

There is a great site you can visit to learn about this stuff
:http://www.practicallynetworked.com/ Here's my lame explanation of your
question: Your isp communicates to one address, which is probably the
address of the computer you used to set up the account. Your router clones
that address so now your isp only communicates with the router. As each
computer is connected to the router it assigns them ip addresses . I find
this stuff really confusing because the use of the term "ip" address means
different things. Such as wan ip address which is the internet side of your
router and lan ip address, which is the address behind the router. Then
there is the default gateway which is the 192.168.x.x of the router itself.
Check out the site and the many links it has. I'm sure it'll clarify some of
this for you











"Johnno" <(E-Mail Removed)> wrote in message
news:42db3a4d$(E-Mail Removed)...
> I'm a newbie who is trying to teach myself a bit more about how things
> work
> on the net, and I have struck a dilemma. Below I will write how I believe
> IP
> addresses work (from what I've read). Please point out where my logic and
> /
> or assumptions have broken down. I'm sure some of you will have fun
> laughing
> at me, but here goes
>
> Every computer must have an IP address to connect to the internet. No two
> computers can hav the same address. When you log on to the net through an
> ISP, each router you log on throgh has it's own address, and your computer
> actually uses that IP address for that session (server assigned IP
> addresses). But then I realize that my router has its' own address, and it
> is static. I can only assume that every router of that model has the same
> address, as it it given in the manual. That flies in the face of my belief
> that no 2 machines can have the same IP address. What huge hole in the
> fabric of my knowledge did I just fall through?
> Johnno.
> Replace "invalid" with ".com.au" to reply.
>
>

Johnno wrote:
> Every computer must have an IP address to connect to the internet. No two
> computers can hav the same address. When you log on to the net through an
> ISP, each router you log on throgh has it's own address, and your computer
> actually uses that IP address for that session (server assigned IP
> addresses). But then I realize that my router has its' own address, and it
> is static. I can only assume that every router of that model has the same
> address, as it it given in the manual. That flies in the face of my belief
> that no 2 machines can have the same IP address. What huge hole in the
> fabric of my knowledge did I just fall through?
> Johnno.

This is a little over-simplified, but perhaps you can get the
basic idea.

Your router has one or more names that are known to machines
on the Internet (DNS machines, maybe others as well) and it
has at least one unique numerical address (maybe more than
one) also known to machines on the Internet. Everything
sent to any computer on your local network has to be sent
to one of those names/addresses known to the Internet.

Your router also has one or more names (usually one) and one
or more numerical addresses (usually one) that are known to
machines on your network. They do not need to be the same
as the names/addresses known to machines on the Internet.
The Internet thinks your router is Bob; your local machines
think your router is Josephine. No problem. (And your local
net can have a router known as Josephine to local machines
and another local net can have a router known to machines on
that local net as Josephine, so long as none of the machines
on either net know about the other Josephine.)

Your router also has to know names/addresses (usually one of
each per computer) for machines on your network. And it
has to read headers for data packets to see where they are
from and where they are going.

The router keeps track of all the above and follows
instructions in its firmware and settings in its configuration
that specify what to do with what. If a machine on your
network contacts a machine on the internet, the router knows
about it and will know where to send the reply from the
machine on the internet. Everything comes and goes through
your router, and it routes everything where it should go.
Therefore, it is called a router.

Things can get a good bit more complicated if machines on
the Internet need to contact a machine on your lan directly,
and yet more complicated when the router takes over the job
of traffic cop enforcing rules about what machines can
communicate with what other machines. The router may refuse
to let any Internet machine initiate a conversation with
any of your local network machines, or it may allow ftp
conections from the Internet but only to a specific computer
on your local net, or it may filter packets based on a set
of rules (send all packets containing the command fsck to
the used bit bag or the null device), or do a bunch of other
things.

But in the simple circumstances described above, the router
has a fairly simple job to do, and it will do it well.
Internet rules try to keep things simple, by specifying
ranges of numerical addresses that may be used on local
nets but that are prohibited from Internet communications.
(Every local net can have one and only one machine with
address 192.168.17.43, because this address is illegal
and will be ignored by machines on the Internet, even
if they see it, which should not happen.) Names likewise
must be unique within the domain in which they may be
seen, but every computer is known as localhost and
has IP address 127.0.0.1 for the processes running on
it. Processes on another computer will have to have
a different name and address for it, or they could not
distinguish between their localhost and and this other
localhost, but communications software and routers take
care of keeping things separate and making sure processes
see and recognize only what they are supposed to see
and recognize.

HTH

jim b.



--
Unix is not user-unfriendly; it merely
expects users to be computer-friendly.

Ok Johnno,

You are correct and wrong at the same time.. now laff at that comment.

Yes every computer that is on the interent HAS to run its own Dynamic IP
unless assigned a Static IP, if you are using a rounter, then your
Static/Dynamic IP is assigned to your Router, and it is different to any
other address assigned. The Router then assigns the PC that it is connected
to a new IP, Normally a network IP (eg. 192.168.*.*) then so the router may
have the ip addess of 202.138.*.* but the pc its self has a networking ip
that is pretty uniform for most networks of 192.168.*.*

So yes Routers do have there own IP address that no one else can have. but
if you do not usea Router and only a modem, then your PC's IP address will
be unique.

Dylan

"Johnno" <(E-Mail Removed)> wrote in message
news:42db3a4d$(E-Mail Removed)...
> I'm a newbie who is trying to teach myself a bit more about how things
> work
> on the net, and I have struck a dilemma. Below I will write how I believe
> IP
> addresses work (from what I've read). Please point out where my logic and
> /
> or assumptions have broken down. I'm sure some of you will have fun
> laughing
> at me, but here goes
>
> Every computer must have an IP address to connect to the internet. No two
> computers can hav the same address. When you log on to the net through an
> ISP, each router you log on throgh has it's own address, and your computer
> actually uses that IP address for that session (server assigned IP
> addresses). But then I realize that my router has its' own address, and it
> is static. I can only assume that every router of that model has the same
> address, as it it given in the manual. That flies in the face of my belief
> that no 2 machines can have the same IP address. What huge hole in the
> fabric of my knowledge did I just fall through?
> Johnno.
> Replace "invalid" with ".com.au" to reply.
>
>

I used to use the DLink modem, and yes it is a free modified version of Zone
Alarm that they use, and it is very basic and cannot be updated, although
they try to get you to buy the real version that installs on your pc, but
still the DLink router does not havea real working up-to-date Fire Wall.

Dylan