Strange outgoing IP settings with router

Hi, I have sort of a newbie question. I noticed this morning, that when
I don't run my cable modem through my router (WRT54G), but right into
my computer I usually get a new IP address that I've never seen before.
Howeer, when I use my router, I end up with the same one I've been
getting with the router for a long time now. This isn't really a
problem I'm just curious as to why
-Chris

On 2006-06-13, (E-Mail Removed) <(E-Mail Removed)> wrote:
> Hi, I have sort of a newbie question. I noticed this morning, that when
> I don't run my cable modem through my router (WRT54G), but right into
> my computer I usually get a new IP address that I've never seen before.
> Howeer, when I use my router, I end up with the same one I've been
> getting with the router for a long time now. This isn't really a
> problem I'm just curious as to why

Your cable provider gives you an internet ip address.

As they have limited resources, and to simplify configuration,
they (your provider) have a pool of IPs and just give out any free
address when you connect.



A router can put multiple computers online over one line.
IP addresses have to be distinctive, but you only get _one_ from your
provider.

So the trick is, your router has two interfaces, internal and external,
and "routes" the IP packages for your PCs.

The routers external interface gets the single ip address from your
provider, you just don't get to see it on your PC.

At the internal interface, it acts as DHCP server, and when your
computer asks for an ip, it gives out one from an internal network
block, e.g. 192.168.1.1 - 192.168.1.255.
Usually, routers remind which internal IP you had last and
reassign it to you on request, so you usually get the same internal
ip address.

--
Marco Dieckhoff
GPG Key 0x1A6C95BA -- http://www.frankonia-brunonia.de/keys

Marco Dieckhoff wrote:
> On 2006-06-13, (E-Mail Removed) <(E-Mail Removed)> wrote:
> > Hi, I have sort of a newbie question. I noticed this morning, that when
> > I don't run my cable modem through my router (WRT54G), but right into
> > my computer I usually get a new IP address that I've never seen before.
> > Howeer, when I use my router, I end up with the same one I've been
> > getting with the router for a long time now. This isn't really a
> > problem I'm just curious as to why
>
> Your cable provider gives you an internet ip address.
>
> As they have limited resources, and to simplify configuration,
> they (your provider) have a pool of IPs and just give out any free
> address when you connect.
>
>
>
> A router can put multiple computers online over one line.
> IP addresses have to be distinctive, but you only get _one_ from your
> provider.
>
> So the trick is, your router has two interfaces, internal and external,
> and "routes" the IP packages for your PCs.
>
> The routers external interface gets the single ip address from your
> provider, you just don't get to see it on your PC.
>
> At the internal interface, it acts as DHCP server, and when your
> computer asks for an ip, it gives out one from an internal network
> block, e.g. 192.168.1.1 - 192.168.1.255.
> Usually, routers remind which internal IP you had last and
> reassign it to you on request, so you usually get the same internal
> ip address.
>
> --
> Marco Dieckhoff
> GPG Key 0x1A6C95BA -- http://www.frankonia-brunonia.de/keys


Thanks Marco, I understand the concept of the internal routing system.
But does this mean even if I go to a page like whatismyip.com that I'll
get a different IP address from what my external IP really is? This
doesn't seem possible as the one I get WITH the router is outside the
local range, it's just weird that it's always the same. It could be
some way that my ISP is responding to my router or something. I've got
cable and its supposed to be dynamic but I had the same IP for a period
of like 2 years way back.

StormFron...@gmail.com wrote:
> Marco Dieckhoff wrote:
> > On 2006-06-13, (E-Mail Removed) <(E-Mail Removed)> wrote:
> > > Hi, I have sort of a newbie question. I noticed this morning, that when
> > > I don't run my cable modem through my router (WRT54G), but right into
> > > my computer I usually get a new IP address that I've never seen before.
> > > Howeer, when I use my router, I end up with the same one I've been
> > > getting with the router for a long time now. This isn't really a
> > > problem I'm just curious as to why
> >
> > Your cable provider gives you an internet ip address.
> >
> > As they have limited resources, and to simplify configuration,
> > they (your provider) have a pool of IPs and just give out any free
> > address when you connect.
> >
> >
> >
> > A router can put multiple computers online over one line.
> > IP addresses have to be distinctive, but you only get _one_ from your
> > provider.
> >
> > So the trick is, your router has two interfaces, internal and external,
> > and "routes" the IP packages for your PCs.
> >
> > The routers external interface gets the single ip address from your
> > provider, you just don't get to see it on your PC.
> >
> > At the internal interface, it acts as DHCP server, and when your
> > computer asks for an ip, it gives out one from an internal network
> > block, e.g. 192.168.1.1 - 192.168.1.255.
> > Usually, routers remind which internal IP you had last and
> > reassign it to you on request, so you usually get the same internal
> > ip address.
> >
> > --
> > Marco Dieckhoff
> > GPG Key 0x1A6C95BA -- http://www.frankonia-brunonia.de/keys
>
>
> Thanks Marco, I understand the concept of the internal routing system.
> But does this mean even if I go to a page like whatismyip.com that I'll
> get a different IP address from what my external IP really is? This
> doesn't seem possible as the one I get WITH the router is outside the
> local range, it's just weird that it's always the same. It could be
> some way that my ISP is responding to my router or something. I've got
> cable and its supposed to be dynamic but I had the same IP for a period
> of like 2 years way back.

--Oh and just to add another little question. The way I have this setup
right now. I run my cable modem into the router, a CAT5 cable into this
PC here, and I've got an antenna for wireless. Last night I went to use
my laptop with the USB adaptor I have and it would just connect to the
local network and not the internet. I came back to my PC here and saw
all these messages about "IP conflicts".. suddenly my cable modem
(Motoralla Surfboard) wouldn't even aquire an IP.. the LEDs wouldn't go
down past flashing on "Recieve". I was wondering if maybe my router
screwed up my ISPs DNS for a while and they blocked me? </rant>

(E-Mail Removed) wrote:
....
>
> --Oh and just to add another little question. The way I have this setup
> right now. I run my cable modem into the router, a CAT5 cable into this
> PC here, and I've got an antenna for wireless. Last night I went to use
> my laptop with the USB adaptor I have and it would just connect to the
> local network and not the internet. I came back to my PC here and saw
> all these messages about "IP conflicts".. suddenly my cable modem
> (Motoralla Surfboard) wouldn't even aquire an IP.. the LEDs wouldn't go
> down past flashing on "Recieve". I was wondering if maybe my router
> screwed up my ISPs DNS for a while and they blocked me? </rant>

Maybe your PC and your router tried to use the same (external)
IP. Try to switch on the modem and the router while your PC is
switched off and then check if your laptop is connecting to the
internet.

Jarek P.