Connecting two PC's with a crossover cable kills the wifi internet.

[just bob]

Connecting two PC's with a crossover cable kills the wifi internet.

When we travel we usually have two laptops connected to the same public WiFi
to check email and surf the web but we also need to share many very large
files between the two laptops. Since both computes have gigabit NIC's I
tried using a crossover cable to link them to get better speeds than over
WiFi.

Both laptops are identical Dell D630 with internal Wifi adapters.

Laptop-A's GB NIC is assigned 172.16.16.1 and Laptop-B is 172.16.16.2,
subnet mask is 255.255.255.0 and gateway is themselves.

When I do this the two PC's see each other just fine but the WiFi to the
internet stops working. I believe it is a routing to default gateway issue
but I'm not sure how to cure this. How do you force the PC to use the WiFi
as the default gateway, if that will solve the problem? I have tried using
the route command but even though I craft the command statement exactly as
the help doc says it comes back with an error.

route add 0.0.0.0 MASK 255.255.0.0 192.168.1.10

If you have any ideas how to make this work please let me know!

Thanks,
-Bob

[John Wunderlich]

Post by just bob
Connecting two PC's with a crossover cable kills the wifi
internet.
When we travel we usually have two laptops connected to the same
public WiFi to check email and surf the web but we also need to
share many very large files between the two laptops. Since both
computes have gigabit NIC's I tried using a crossover cable to
link them to get better speeds than over WiFi.
Both laptops are identical Dell D630 with internal Wifi adapters.
Laptop-A's GB NIC is assigned 172.16.16.1 and Laptop-B is
172.16.16.2, subnet mask is 255.255.255.0 and gateway is
themselves.
When I do this the two PC's see each other just fine but the WiFi
to the internet stops working. I believe it is a routing to
default gateway issue but I'm not sure how to cure this. How do
you force the PC to use the WiFi as the default gateway, if that
will solve the problem? I have tried using the route command but
even though I craft the command statement exactly as the help doc
says it comes back with an error.
route add 0.0.0.0 MASK 255.255.0.0 192.168.1.10
If you have any ideas how to make this work please let me know!
Thanks,
-Bob

Difficult to say for sure without setting up my computer but check
your "route print" output and see if you have two lines that have
Destination 0.0.0.0 mask 0.0.0.0. There will probably be one for
each network connection that is working. Check the "Metric" column.
Wireless networks usually have a metric of 25 and wired networks a
metric of 1. The metric of "1" will be used before the metric of
"25". You probably need to change this around so that your wireless
connection has a metric of 1 and your wired network a metric of 25.
To do this, you will probably have to enter lines something like the
following:

route change 0.0.0.0 mask 0.0.0.0 172.16.16.1 metric 25
route change 0.0.0.0 mask 0.0.0.0 192.168.1.1 metric 1

where the "172.16.16.1" and "192.168.1.1" are the Gateway addresses
that currently appear in your "route print" output.

Good Luck,
John

[Kurt]

Post by just bob
Connecting two PC's with a crossover cable kills the wifi internet.
When we travel we usually have two laptops connected to the same public WiFi
to check email and surf the web but we also need to share many very large
files between the two laptops. Since both computes have gigabit NIC's I
tried using a crossover cable to link them to get better speeds than over
WiFi.
Both laptops are identical Dell D630 with internal Wifi adapters.
Laptop-A's GB NIC is assigned 172.16.16.1 and Laptop-B is 172.16.16.2,
subnet mask is 255.255.255.0 and gateway is themselves.
When I do this the two PC's see each other just fine but the WiFi to the
internet stops working. I believe it is a routing to default gateway issue
but I'm not sure how to cure this. How do you force the PC to use the WiFi
as the default gateway, if that will solve the problem? I have tried using
the route command but even though I craft the command statement exactly as
the help doc says it comes back with an error.
route add 0.0.0.0 MASK 255.255.0.0 192.168.1.10
If you have any ideas how to make this work please let me know!
Thanks,
-Bob

Because you have a gateway. The default gateway specified manually has a
precedence over the DHCP gateway you get from the wireless. Multiple
default gateways works OK if only one or the other connections is active
at any given time, but will fail (as you can see) if the gateway is
available but has no path to the Internet. Since you are just connecting
the two computers, you have no need for a default gateway on the Gig
NICs. Just remove the gateways from the configs and everything will work
just fine. Also, for the sake of security, you should disable Client for
Microsoft Networks and File and Print Sharing on the wireless.

Kurt