How do I fix the problem of 'duplicate IP address' ?

O

O Noah

Explanation :-
I have a DSL modem (SpeedStream), and its output RJ-45 is
plugged into a Ethernet switch (D-link DSS-5+, 10/100 Mbits).
From the Ethernet Switch first output is plugged into my
'gateway' PC, and the second output is plugged into a Wireless
Router (D-link DI-524). The 'gateway' PC is the local server
for the rest of my home PCs. I keep the Wireless Router on
all the time, to connect the Wireless once in a while, through a
D-Link Wireless Cardbus Adapter (DWL-650) for my Laptop.
Since this was the easiest way to keep snoopers out of the
home network, for sometime all was working well.

Problem :-
Now when I turn on the Laptop, the common 'gateway' server
complains that it cannot serve a duplicate IP address, which is
(198.168.0.100), and the Internet stops on all PCs and the
Laptop.

The local file transfer works. The IP address happens to be the
Laptop's IP address, created by the Cardbus Adapter within
the Laptop. The remaining PCs are using different IP addresses
and the number of the 'gateway' is (198.168.0.1) as usual.
Gateway also has a regular IP for the DSLs address.

I wonder why does the 'gateway' pc sometime complains about
the duplicate IP address but as soon as I turn off the Laptop,
it quits complaining.

Help :-
Is there a way to re-allocate the IP address on the Laptop,
if so, do I need to remove and then re-load the CardBus
Adapter Software, or there is an easy way to do this?

Any suggestion will be highly appreciated.
 
J

John R Weiss

O Noah said:
Explanation :-
I have a DSL modem (SpeedStream), and its output RJ-45 is
plugged into a Ethernet switch (D-link DSS-5+, 10/100 Mbits).
From the Ethernet Switch first output is plugged into my
'gateway' PC, and the second output is plugged into a Wireless
Router (D-link DI-524). The 'gateway' PC is the local server
for the rest of my home PCs. I keep the Wireless Router on
all the time, to connect the Wireless once in a while, through a
D-Link Wireless Cardbus Adapter (DWL-650) for my Laptop.

You should have the DSL modem connected to the router, then everything else
downstream of that. If the router is wireless only (a Wireless Access Point
instead of a Wired/Wireless router) replace it with a proper router.

Since this was the easiest way to keep snoopers out of the
home network, for sometime all was working well.

Nope. Your wired segment is unprotected. It may work, but is very vulnerable,
especially if your DSL connection is via a static IP address.

Problem :-
Now when I turn on the Laptop, the common 'gateway' server
complains that it cannot serve a duplicate IP address, which is
(198.168.0.100), and the Internet stops on all PCs and the
Laptop.

The DHCP server in your router may be serving an address that you also are using
in your wired segment.

The local file transfer works. The IP address happens to be the
Laptop's IP address, created by the Cardbus Adapter within
the Laptop. The remaining PCs are using different IP addresses
and the number of the 'gateway' is (198.168.0.1) as usual.
Gateway also has a regular IP for the DSLs address.

I wonder why does the 'gateway' pc sometime complains about
the duplicate IP address but as soon as I turn off the Laptop,
it quits complaining.

How is your "gateway" computer serving the rest of your wired network?

Help :-
Is there a way to re-allocate the IP address on the Laptop,
if so, do I need to remove and then re-load the CardBus
Adapter Software, or there is an easy way to do this?

Any suggestion will be highly appreciated.

Correct your network topology so all computers are behind a single router.
 
O

O Noah

Thank you for the excellent suggestions. You are absolutely right,
about the static IP address, but I am used to it, and have tripple
set of protections, such as firewall and other stuff for each PC &
the Laptop. We had this setup since later part of 1999, and still
working OK. Trouble started just days ago.

Well, so far all I did is, reload software for the D-Link DWL-650
Cardbus Adapter for my Laptop, and it is working OK now !
Thanks again for your comments.

| > Explanation :-
| > I have a DSL modem (SpeedStream), and its output RJ-45 is
| > plugged into a Ethernet switch (D-link DSS-5+, 10/100 Mbits).
| > From the Ethernet Switch first output is plugged into my
| > 'gateway' PC, and the second output is plugged into a Wireless
| > Router (D-link DI-524). The 'gateway' PC is the local server
| > for the rest of my home PCs. I keep the Wireless Router on
| > all the time, to connect the Wireless once in a while, through a
| > D-Link Wireless Cardbus Adapter (DWL-650) for my Laptop.
|
| You should have the DSL modem connected to the router, then everything else
| downstream of that. If the router is wireless only (a Wireless Access Point
| instead of a Wired/Wireless router) replace it with a proper router.
|
|
| > Since this was the easiest way to keep snoopers out of the
| > home network, for sometime all was working well.
|
| Nope. Your wired segment is unprotected. It may work, but is very vulnerable,
| especially if your DSL connection is via a static IP address.
|
|
| > Problem :-
| > Now when I turn on the Laptop, the common 'gateway' server
| > complains that it cannot serve a duplicate IP address, which is
| > (198.168.0.100), and the Internet stops on all PCs and the
| > Laptop.
|
| The DHCP server in your router may be serving an address that you also are using
| in your wired segment.
|
|
| > The local file transfer works. The IP address happens to be the
| > Laptop's IP address, created by the Cardbus Adapter within
| > the Laptop. The remaining PCs are using different IP addresses
| > and the number of the 'gateway' is (198.168.0.1) as usual.
| > Gateway also has a regular IP for the DSLs address.
| >
| > I wonder why does the 'gateway' pc sometime complains about
| > the duplicate IP address but as soon as I turn off the Laptop,
| > it quits complaining.
|
| How is your "gateway" computer serving the rest of your wired network?
|
|
| > Help :-
| > Is there a way to re-allocate the IP address on the Laptop,
| > if so, do I need to remove and then re-load the CardBus
| > Adapter Software, or there is an easy way to do this?
| >
| > Any suggestion will be highly appreciated.
|
| Correct your network topology so all computers are behind a single router.
|
|
 
G

Guest

I am glad it is working again but John is correct that your network topology
is unorthodox. You actually appear to have two separate networks running
side-by-side. Your wireless router must have DHCP running and is issuing IP
addresses to any wireless PCs, and likewise your Gateway PC is acting as a
DHCP server and is issuing IPs to any PCs linked through it. Unless you set
this up carefully to prevent overlap of the IP addresses issued you can have
the situation where both DHCP servers issue the same IP address to two
different PCs. If the network doesnt change much it will hang together once
different IPs are given but it may fall over again with any change to the IP
assignment.

This how I have set up my mini-network:

ADSL modem -> router (192.168.1.1 range) -> "gateway" SBServer 2003
(192.168.0.1 range for LAN clients, 192.168.1.2 on router side)->switch/hub->
wireless AP with distinct IP and all other PCs (192.168.0.1 range)

This way the PCs and the wireless AP all take advantage of the servers
gateway firewall as well as the NAT offered by the router (as well as a
software firewall).
If I want non-authenticated access to the internet (customer PCs) I plug in
directly to the router

In your case you could substitute the router for your wireless router
(wireless access would be outside the control of the gateway PC)

Peter G
 
O

O Noah

Hello Peter,

Just few minutes ago SBC technician came by and tested all of our phone
outlets and the line traps and found one phone outlet bad (highly resistive
due to rusting but not fully shorted). Our DSL speed supposed to be at
3 Mbps range, but it was running barely 1.2 Mbps. After replacing the
phone outlet the DSL is running at 2.5 Mbps now. We are about 1.5 mile
away from the phone exchange.

Friend of mine is a professor of Electronics Engineering at the local university.
He helped the way our network is set up. Apparantly he does not trust the
'Wireless' systems, neither do we.

Yes, the 'wireless' router does have DHCP running and the Gateway PC is also
acting as a DHCP server thru hard wired lines. It is serving the rest of our PCs
thru phoneline network. (Yes we do run Zone Alarm, AVG, Norton AntiVirus,
Ad-Aware, SpyBot Spy Blocker and Microsoft AntiSpyware on each PC).

The reason for setting a double network at home is this - we have a grown up
kid who needs to be on a different network with his friends and their Laptops.
As soon as they come to visit us, at our home, they should not have facilities to
view and transfer files form our PCs to their Laptops. I am sure one of these
days they will find a way thru VPN or something else. But until then we are
'secure'. You are absolutely right, we want keep the wireless access outside
the control of the gateway PC and the home network. We transfer files thru
USB ports of the Laptops and PCs which is coupled temporarily.

Thank you so much.

O Noah

|I am glad it is working again but John is correct that your network topology
| is unorthodox. You actually appear to have two separate networks running
| side-by-side. Your wireless router must have DHCP running and is issuing IP
| addresses to any wireless PCs, and likewise your Gateway PC is acting as a
| DHCP server and is issuing IPs to any PCs linked through it. Unless you set
| this up carefully to prevent overlap of the IP addresses issued you can have
| the situation where both DHCP servers issue the same IP address to two
| different PCs. If the network doesnt change much it will hang together once
| different IPs are given but it may fall over again with any change to the IP
| assignment.
|
| This how I have set up my mini-network:
|
| ADSL modem -> router (192.168.1.1 range) -> "gateway" SBServer 2003
| (192.168.0.1 range for LAN clients, 192.168.1.2 on router side)->switch/hub->
| wireless AP with distinct IP and all other PCs (192.168.0.1 range)
|
| This way the PCs and the wireless AP all take advantage of the servers
| gateway firewall as well as the NAT offered by the router (as well as a
| software firewall).
| If I want non-authenticated access to the internet (customer PCs) I plug in
| directly to the router
|
| In your case you could substitute the router for your wireless router
| (wireless access would be outside the control of the gateway PC)
|
| Peter G
|
|
|
| "O Noah" wrote:
|
| > Thank you for the excellent suggestions. You are absolutely right,
| > about the static IP address, but I am used to it, and have tripple
| > set of protections, such as firewall and other stuff for each PC &
| > the Laptop. We had this setup since later part of 1999, and still
| > working OK. Trouble started just days ago.
| >
| > Well, so far all I did is, reload software for the D-Link DWL-650
| > Cardbus Adapter for my Laptop, and it is working OK now !
| > Thanks again for your comments.
| >
| > | > | > Explanation :-
| > | > I have a DSL modem (SpeedStream), and its output RJ-45 is
| > | > plugged into a Ethernet switch (D-link DSS-5+, 10/100 Mbits).
| > | > From the Ethernet Switch first output is plugged into my
| > | > 'gateway' PC, and the second output is plugged into a Wireless
| > | > Router (D-link DI-524). The 'gateway' PC is the local server
| > | > for the rest of my home PCs. I keep the Wireless Router on
| > | > all the time, to connect the Wireless once in a while, through a
| > | > D-Link Wireless Cardbus Adapter (DWL-650) for my Laptop.
| > |
| > | You should have the DSL modem connected to the router, then everything else
| > | downstream of that. If the router is wireless only (a Wireless Access Point
| > | instead of a Wired/Wireless router) replace it with a proper router.
| > |
| > |
| > | > Since this was the easiest way to keep snoopers out of the
| > | > home network, for sometime all was working well.
| > |
| > | Nope. Your wired segment is unprotected. It may work, but is very vulnerable,
| > | especially if your DSL connection is via a static IP address.
| > |
| > |
| > | > Problem :-
| > | > Now when I turn on the Laptop, the common 'gateway' server
| > | > complains that it cannot serve a duplicate IP address, which is
| > | > (198.168.0.100), and the Internet stops on all PCs and the
| > | > Laptop.
| > |
| > | The DHCP server in your router may be serving an address that you also are using
| > | in your wired segment.
| > |
| > |
| > | > The local file transfer works. The IP address happens to be the
| > | > Laptop's IP address, created by the Cardbus Adapter within
| > | > the Laptop. The remaining PCs are using different IP addresses
| > | > and the number of the 'gateway' is (198.168.0.1) as usual.
| > | > Gateway also has a regular IP for the DSLs address.
| > | >
| > | > I wonder why does the 'gateway' pc sometime complains about
| > | > the duplicate IP address but as soon as I turn off the Laptop,
| > | > it quits complaining.
| > |
| > | How is your "gateway" computer serving the rest of your wired network?
| > |
| > |
| > | > Help :-
| > | > Is there a way to re-allocate the IP address on the Laptop,
| > | > if so, do I need to remove and then re-load the CardBus
| > | > Adapter Software, or there is an easy way to do this?
| > | >
| > | > Any suggestion will be highly appreciated.
| > |
| > | Correct your network topology so all computers are behind a single router.
| > |
| > |
| >
| >
| >
 
G

Guest

Now I understand!

The trouble caused by our sons ... cant we trade them in or something :)

Peter G
 

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