IP adress conflict in a "in-line" network

C

CFran

Here is how my network is setup like :

Modem<--->PC #1<--->PC #2<--->PC #3 (all my PC's are under Windows XP
and connected by Ethernet)

I'm aware that this is not the best configuration, but this is what I
have to deal with.

My problem is this : I can share my internet connection from PC #1 so I
can access internet from PC #2, but when i try to activate the
connection sharing on PC #2 so PC #3 can access internet too, it
complains about an IP adress conflict (I think it means that both PC #2
and PC #3 try to have the same IP, but I'm not sure) and it prevents me
from sharing the connection from PC #2 to PC #3.

Is it just not possible to share the connection from PC #2 to PC #3 in
this configuration with Windows XP, or what do I have to do to make it
work?
 
C

chrispsg

ICS sets your a default IP address of 192.168.1.1 if memory server me
right. What is happening is when you turn on ICS on PC 2 that address
is set to the NIC in PC2 resulting in the IP Conflict. You shouldnt
have to turn on ICS for PC2. You need ICS on PC1 and then connect them
all together with a switch.

hope this helps,
psg
 
C

CFran

chrispsg said:
ICS sets your a default IP address of 192.168.1.1 if memory server me
right. What is happening is when you turn on ICS on PC 2 that address
is set to the NIC in PC2 resulting in the IP Conflict. You shouldnt
have to turn on ICS for PC2. You need ICS on PC1 and then connect them
all together with a switch.

hope this helps,
psg
Click to expand...

with a switch? so you mean I can't connect them the way it is right now?
 
K

Kurt

You can probably get it to work as far as sharing Internet, but you will not
have a LAN (you won't be able to have duplex connectivity between computers
1 & 3). ICS automagically assigns an IP address of 192.168.0.1 to the
"private" interface (see below) of any computer when it is first enabled.
ICS is a router. Routers forward packets between different networks. So
you'll need 3 distinct networks (not counting your public Internet address).
Let's choose 192.168.1.1, 192.168.2.1, and 192.168.3.1.

Internet
|
65.123.234.101 or whatever
Router
192.168.1.1
|
192.168.1.2 (Public)
Computer 1
192.168.2.1 (Private)
|
192.168.2.2 (Public)
Computer 2
192.168.3.1 (Private)
|
192.168.3.2
Computer 3

Remember, all 3 networks must be unique. So the actual networks you choose
will depend on what your router's private network is. I'll assume the
networks I have listed here, and you can sub them as necessary.

The following assumes computer 1 can connect to the Internet.

First, configure Computer1 for ICS. Then change the IP address of the
private NIC to 192.168.2.1. ICS won't care. The only thing that won't work
is the DHCP server (with only 3 computers, so what). Assign the IP address
of 192.168.2.2 to the public NIC on computer 2. The IP settings are:

Address: 192.168.2.2
Mask: 255.255.255.0
G/W 192.168.2.1
DNS: <your ISPs DNS Server Address(es)>

Then enable ICS on computer 2. Change the IP address of the private side of
computer 2 to 192.168.3.1

Configure computer 3 as such

Address: 192.168.3.2
Mask: 255.255.255.0
G/W 192.168.3.1
DNS: <your ISPs DNS Server Address(es)>

You should have Internet on all 3 computers. You will be triple NATed, so
there is the possibility that some things won't work right or get confused,
but I doubt it.

....kurt
 
C

chrispsg

The optimal configuration would be to use a switch. The config would be
as follows.

PC1-Internet Connection via modem using Internet Connection
Sharing.Connected to switch.
PC2-PC3-Connect network cards to switch.

ICS from PC1 would provide an internet connection to all PC's on the
network.

I am not sure how you have them connected together right now. But what
I do know is that it is not necassary to have ICS turned on for two
pc's on the network.

let me know if this helps,
psg
 
C

CFran

Kurt said:
You can probably get it to work as far as sharing Internet, but you will not
have a LAN (you won't be able to have duplex connectivity between computers
1 & 3). ICS automagically assigns an IP address of 192.168.0.1 to the
"private" interface (see below) of any computer when it is first enabled.
ICS is a router. Routers forward packets between different networks. So
you'll need 3 distinct networks (not counting your public Internet address).
Let's choose 192.168.1.1, 192.168.2.1, and 192.168.3.1.

Internet
|
65.123.234.101 or whatever
Router
192.168.1.1
|
192.168.1.2 (Public)
Computer 1
192.168.2.1 (Private)
|
192.168.2.2 (Public)
Computer 2
192.168.3.1 (Private)
|
192.168.3.2
Computer 3

Remember, all 3 networks must be unique. So the actual networks you choose
will depend on what your router's private network is. I'll assume the
networks I have listed here, and you can sub them as necessary.

The following assumes computer 1 can connect to the Internet.

First, configure Computer1 for ICS. Then change the IP address of the
private NIC to 192.168.2.1. ICS won't care. The only thing that won't work
is the DHCP server (with only 3 computers, so what). Assign the IP address
of 192.168.2.2 to the public NIC on computer 2. The IP settings are:

Address: 192.168.2.2
Mask: 255.255.255.0
G/W 192.168.2.1
DNS: <your ISPs DNS Server Address(es)>

Then enable ICS on computer 2. Change the IP address of the private side of
computer 2 to 192.168.3.1

Configure computer 3 as such

Address: 192.168.3.2
Mask: 255.255.255.0
G/W 192.168.3.1
DNS: <your ISPs DNS Server Address(es)>

You should have Internet on all 3 computers. You will be triple NATed, so
there is the possibility that some things won't work right or get confused,
but I doubt it.

...kurt
Click to expand...

Your solution works perfectly. Thank you Kurt.
 
K

Kurt

Yes, psg has supplied the preferred setup. In the setup on his link you
would have a true LAN, where you could share files and printers as well as
Internet. My solution is a stopgap based solely on your assertion that this
is the only way you can hook it up. A switch nowadays can be had for around
$35 US and a router (which will also take care of assigning IP addresses
automatically) for just a littlt more. For stability and independence
(computer 3 won't have Internet unless the other two are up and running),
the investment would be worthwhile.

....kurt
 
C

CFran

Kurt said:
Yes, psg has supplied the preferred setup. In the setup on his link you
would have a true LAN, where you could share files and printers as well as
Internet. My solution is a stopgap based solely on your assertion that this
is the only way you can hook it up. A switch nowadays can be had for around
$35 US and a router (which will also take care of assigning IP addresses
automatically) for just a littlt more. For stability and independence
(computer 3 won't have Internet unless the other two are up and running),
the investment would be worthwhile.

...kurt
Click to expand...

yeah, i know that my configuration really ain't the best thing, but if
I gotta do it like this it's because the cable from computer 2 to
computer 3 is too short to go from computer 3 to 1, and i really don't
feel like buying one more 30 metres long cable just for that. As for
file sharing and all that, it doesn't matter, cuz I can't even get it
to work properly with only two computers (I send files by instant
messaging instead, it goes about as fast, like 4 MB/s)
 
T

Tony

CFran said:
yeah, i know that my configuration really ain't the best thing, but if
I gotta do it like this it's because the cable from computer 2 to
computer 3 is too short to go from computer 3 to 1, and i really don't
feel like buying one more 30 metres long cable just for that. As for
file sharing and all that, it doesn't matter, cuz I can't even get it
to work properly with only two computers (I send files by instant
messaging instead, it goes about as fast, like 4 MB/s)
Click to expand...

Use a Proxy server on PC2 such as CCProxy free from
http://www.youngzsoft.net/ccproxy/
 
C

CFran

Tony said:
Use a Proxy server on PC2 such as CCProxy free from
http://www.youngzsoft.net/ccproxy/
Click to expand...

I remember the time (not so long ago) when I used to connect PC2 with a
prxy (Proxy+ on PC1). That's cool for the web, but when it comes tu
stuff like eMule it's really crappy, and it prevents you from playing
most online games.

Really, trust me, if you'll want to use a proxy ONLY if you can't work
ICS out. Anyways, as I said a little above, now the problem is fixed,
thanx to the advice of Kurt. Thanks for advice anyways
 

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