Piggy-backing a PC onto a network

I have a 2 PC wireless network set up at home.

I'm forever fixing other people's computers and was sick of unplugging all
my cables from the upstairs one to connect to the other machine when
installing etc. So I bought a KVM switch to give me a spare set of cables
and this system works a treat.

However, I thought while I was doing this, I may as well use my PC's
internet connection to install all the updates etc. and thought it would be
as simple as using a cross-over cable (after all the network socket is spare
due to the wireless). When I do this, my PC seems to lose it's connection
to the net and I can't work out why!

Please help!!

Nel wrote in
jHCNg.8530$(E-Mail Removed):

> I have a 2 PC wireless network set up at home.
>
> I'm forever fixing other people's computers and was sick of
> unplugging all my cables from the upstairs one to connect to the
> other machine when installing etc. So I bought a KVM switch to give
> me a spare set of cables and this system works a treat.
>
> However, I thought while I was doing this, I may as well use my PC's
> internet connection to install all the updates etc. and thought it
> would be as simple as using a cross-over cable (after all the network
> socket is spare due to the wireless). When I do this, my PC seems to
> lose it's connection to the net and I can't work out why!

You need to use a straight-through rather than crossover cable. Some routers
are autosensing and can use either cable but others can't. Best to try with
the correct cable - these are the bog standard Ethernet cables sold by PC
World etc and supplied with many routers.

If it still happens, you need to investigate further:

At wireless PC, with wired PC disconnected:

- Start | Run | cmd
- At C:> prompt: ipconfig
- Check for sensible IP address - typically 192.169.x.y
- Check for sensible gateway address - typically 192.168.x.1 (where x is
same as for IP)
- At C:> prompt, ping 192.168.x.1 (ie the gateay address)
- ping news.bbc.co.uk
- Both pings should give 4 "reply from" responses.

Repeat at wireless PC after wired is connected

Repeat at wired PC


The wireless PC should give the same ping and ipconfig results no matter
whether or not wired PC is connected. Wired PC's IP address should differ
from wireless one's only in the final byte (the "y").

Nel wrote:
> I have a 2 PC wireless network set up at home.
>
> I'm forever fixing other people's computers and was sick of unplugging all
> my cables from the upstairs one to connect to the other machine when
> installing etc. So I bought a KVM switch to give me a spare set of cables
> and this system works a treat.
>
> However, I thought while I was doing this, I may as well use my PC's
> internet connection to install all the updates etc. and thought it would be
> as simple as using a cross-over cable (after all the network socket is spare
> due to the wireless). When I do this, my PC seems to lose it's connection
> to the net and I can't work out why!
>
> Please help!!
>
>
I often do the above. Use a straight through cable. You may
need to go into IE and check "never dial a connction" if the
PC has a dialup connection. Otherwise it will try to dial up
instead of using the router.

RobD wrote in
(E-Mail Removed):

> Nel wrote:
>> I have a 2 PC wireless network set up at home.
>>
>> I'm forever fixing other people's computers and was sick of
>> unplugging all my cables from the upstairs one to connect to the
>> other machine when installing etc. So I bought a KVM switch to give
>> me a spare set of cables and this system works a treat.
>>
>> However, I thought while I was doing this, I may as well use my PC's
>> internet connection to install all the updates etc. and thought it
>> would be as simple as using a cross-over cable (after all the
>> network socket is spare due to the wireless). When I do this, my PC
>> seems to lose it's connection to the net and I can't work out why!
>>
>> Please help!!
>>
>>
> I often do the above. Use a straight through cable. You may
> need to go into IE and check "never dial a connction" if the
> PC has a dialup connection. Otherwise it will try to dial up
> instead of using the router.

One other thing I forgot in my earlier suggestions: make sure that the PC
that you are connecting is set to get its IP and DNS server IPs
automatically, rather than have static addresses set. Unless the static
addresses happened to be in the correct subnet for the router and not
already in use via DHCP on other PCs, you'd get either Destination
Unreachable or else a clash of IP addresses. The default for Windows is for
network devices to be set to automatic, so it's only a problem if someone
has explicitly set static addresses already.

"Martin Underwood" <a@b> wrote in message
news:450709d4$0$3611$(E-Mail Removed)...
> Nel wrote in
> jHCNg.8530$(E-Mail Removed):
>
>> I have a 2 PC wireless network set up at home.
>>
>> I'm forever fixing other people's computers and was sick of
>> unplugging all my cables from the upstairs one to connect to the
>> other machine when installing etc. So I bought a KVM switch to give
>> me a spare set of cables and this system works a treat.
>>
>> However, I thought while I was doing this, I may as well use my PC's
>> internet connection to install all the updates etc. and thought it
>> would be as simple as using a cross-over cable (after all the network
>> socket is spare due to the wireless). When I do this, my PC seems to
>> lose it's connection to the net and I can't work out why!
>
> You need to use a straight-through rather than crossover cable.
I always thought that PC - PC connection required a cross-over cable?

> Some routers are autosensing and can use either cable but others can't.
> Best to try with the correct cable - these are the bog standard Ethernet
> cables sold by PC World etc and supplied with many routers.
>
> If it still happens, you need to investigate further:
>
> At wireless PC, with wired PC disconnected:
>
> - Start | Run | cmd
> - At C:> prompt: ipconfig
> - Check for sensible IP address - typically 192.169.x.y
> - Check for sensible gateway address - typically 192.168.x.1 (where x is
> same as for IP)
> - At C:> prompt, ping 192.168.x.1 (ie the gateay address)
> - ping news.bbc.co.uk
> - Both pings should give 4 "reply from" responses.
>
> Repeat at wireless PC after wired is connected
>
> Repeat at wired PC
>
> The wireless PC should give the same ping and ipconfig results no matter
> whether or not wired PC is connected. Wired PC's IP address should differ
> from wireless one's only in the final byte (the "y").

Cheers, I'll give all that a try!

"Nel" <(E-Mail Removed)> wrote in message
news:jHCNg.8530$(E-Mail Removed)...
>I have a 2 PC wireless network set up at home.
>
> I'm forever fixing other people's computers
[snip]
> I may as well use my PC's internet connection to install all the updates
> etc. and thought it would be as simple as using a cross-over cable (after
> all the network socket is spare due to the wireless).

First, to answer the question you asked elsewhere in the thread, a PC to PC
connection usually does need a cross-over cable (with gigabit cards, and
maybe some 10/100 cards, a straight cable will work). Martin Underwood seems
to be assuming you are plug the computer into the router.

As far as connectivity for the to-be-fixed computer goes, plugging it into
the router is the simplest solution. But I guess this is not a practical
option.

The next simplest thing, if you are running Windows XP on your PC, is to
bridge the wired and wireless interfaces of your PC. However, I have read
that this sometimes does not work correctly if the bridge involves a
wireless adaptor.

A third possible option is to set up Internet Connection Sharing (ICS) to
share the wireless connection. You may need to change the router's
configuration for this to work.

> When I do this, my PC seems to lose it's connection to the net and I can't
> work out why!

This might happen if ICS is enabled on the to-be-fixed PC (ie, to share an
ADSL or dial-up modem normally attached to it). Please post the output of
executing ipconfig (as Martin Underwood described) on your PC both under
normal conditions and when it is in this state.

It is perhaps worth pointing out that you should avoid connecting the PC to
your network (by any method above) unless you are confident it is free of
any virus/worm infections.

Alex

Alex Fraser wrote in
(E-Mail Removed):

> "Nel" <(E-Mail Removed)> wrote in message
> news:jHCNg.8530$(E-Mail Removed)...
>> I have a 2 PC wireless network set up at home.
>>
>> I'm forever fixing other people's computers
> [snip]
>> I may as well use my PC's internet connection to install all the
>> updates etc. and thought it would be as simple as using a cross-over
>> cable (after all the network socket is spare due to the wireless).
>
> First, to answer the question you asked elsewhere in the thread, a PC
> to PC connection usually does need a cross-over cable (with gigabit
> cards, and maybe some 10/100 cards, a straight cable will work).
> Martin Underwood seems to be assuming you are plug the computer into
> the router.

Yes I was. Unless there's a very good reason, I wouldn't recommend any other
way of doing it:

router ------- by wireless ------- your own PC
|
+------------by Ethernet ------- PC to be connected temporarily

is much better and less likely to give problems than:

router ------- by wireless ------- your own PC
|
|
Ethernet
|
|
PC to be connected temporarily


The main problem with using ICS is that it is fixed (as far as I am aware)
to use 192.168.0.1 for the LAN card in your PC and an address in the subnet
192.168.0.x for the temporary PC. It is likely that the router will be
handing out very similar addresses for your PC's wireless card address. You
will certainly have to change the router to use a subnet other than
192.168.0.x (192.168.1.x would be fine) because the router's own address
will probably be 192.168.y.1 (for some value of y) and having both the
router and the temporary PC on the same address (192.168.0.1) would be Bad
News. Even if you use 192.168.1.x subnet, ICS may or may not work: it may be
designed to only to route between a Class A, B or C address (as you'd have
if you connected your PC to a broadband or dial-up modem) and a non-routable
192.168 type address; it may not work between one non-routable address and
another.

Sorry, I know that's all a bit technical. I may be worrying about nothing,
but my gut feeling is that it won't work.

Perhaps someone with more knowledge of TCP can clarify whether I'm right
about ICS's ability to route between (for example) 192.169.1.x and
192.168.0.x subnets. I ask because I've got a customer who was trying to do
exactly what you describe, and ICS wasn't routing the traffic. I replaced
the topology with a wireless card in the remote PC, which allows both PCs to
access the internet and to access each other's shares, but has a frustrating
side-effect for the customer: the PC which owns network shares needs to be
logged in (rather than left at the logon prompt) in order for the other PC
to access the shares, because the wireless card software is only activated
*after* the "server" PC has logged in. If I can get ICS to work, it would
remove this restriction.

"Martin Underwood" <a@b> wrote in message
news:45092081$0$582$(E-Mail Removed)...
[snip]
> The main problem with using ICS is that it is fixed (as far as I am aware)
> to use 192.168.0.1 for the LAN card in your PC and an address in the
> subnet 192.168.0.x for the temporary PC.

At least, there is no obvious way to change it.

> It is likely that the router will be handing out very similar addresses
> for your PC's wireless card address. You will certainly have to change the
> router to use a subnet other than 192.168.0.x (192.168.1.x would be fine)
> because the router's own address will probably be 192.168.y.1 (for some
> value of y) and having both the router and the temporary PC on the same
> address (192.168.0.1) would be Bad News.

The problem is more general than that: which interface should be used to
reach 192.168.0.anything?

> Even if you use 192.168.1.x subnet, ICS may or may not work: it may be
> designed to only to route between a Class A, B or C address (as you'd have
> if you connected your PC to a broadband or dial-up modem) and a non-
> routable 192.168 type address; it may not work between one non-routable
> address and another.

I have not tried it, but there is no reason for ICS to care. But if it does,
it would not be the first networking-related stupidity I have seen in
Microsoft software.

> Perhaps someone with more knowledge of TCP can clarify whether I'm right
> about ICS's ability to route between (for example) 192.169.1.x and
> 192.168.0.x subnets. I ask because I've got a customer who was trying to
> do exactly what you describe, and ICS wasn't routing the traffic. I
> replaced the topology with a wireless card in the remote PC, which allows
> both PCs to access the internet and to access each other's shares, but has
> a frustrating side-effect for the customer: the PC which owns network
> shares needs to be logged in (rather than left at the logon prompt) in
> order for the other PC to access the shares, because the wireless card
> software is only activated *after* the "server" PC has logged in.

Is the PC with the shares running Windows XP, and if so, is there a reason
why you are using "the wireless card software" rather than Windows' built-in
equivalent? With the latter, I believe the wireless network connection is
established before logon (I am unable to check at the moment).

Alex

"Alex Fraser" <(E-Mail Removed)> wrote in message
news:LvWdnbeMG-(E-Mail Removed)...
[snip]
> Is the PC with the shares running Windows XP, and if so, is there a reason
> why you are using "the wireless card software" rather than Windows'
> built-in equivalent? With the latter, I believe the wireless network
> connection is established before logon (I am unable to check at the
> moment).

....but I am able to check now, and it is .

Alex

Alex Fraser wrote in
te-(E-Mail Removed):

> "Alex Fraser" <(E-Mail Removed)> wrote in message
> news:LvWdnbeMG-(E-Mail Removed)...
> [snip]
>> Is the PC with the shares running Windows XP, and if so, is there a
>> reason why you are using "the wireless card software" rather than
>> Windows' built-in equivalent? With the latter, I believe the
>> wireless network connection is established before logon (I am unable
>> to check at the moment).
>
> ...but I am able to check now, and it is .

Brilliant news! It's a Netgear WG111 that the customer is using and the
default installation uses Netgear's own software to control the wireless
adaptor. It never occurred to me to change to the Windows Zero Config
software instead, because I thought that would be subject to the same
restriction. Evidently not.

I'll give my customer a ring tomorrow and arrange to try it out so see if it
solves her problem.