Why can't I see a computer on my network?

[Sandy]

A few weeks ago, I set up a home network using a Linksys BEFW11S4
Router. My desktop(call it A) is directly connected to the router.
I have a second desktop (call it B) connected via a Wireless PCI card
and a laptop directly connected. The laptop is for work and has a
different group name than the other two computers and can't be seen by
either computer A or computer B, which is expected..

Until recently, I could access computer B from computer A. Now I
can't. They both belong to group MSHOME. Computer B has no problem
sharing the internet connection, but if I ping computer A from it, I
get no response. WEP is enabled and I checked the encryption and it
looks correct on both ends. Boith are enabled, 64-bit, with the same
encryption key. If I check the DHCP clients table, computer A shows up
and so does the laptop, but not computer B. Also, I cannot ping
computer B from computer A.

I can't think what else to check. I can't think of what I could have
done to change the network configuration. I'm at wits end. What am I
missing?

 

[Paul Landregan]

A few weeks ago, I set up a home network using a Linksys BEFW11S4
Router. My desktop(call it A) is directly connected to the router.
I have a second desktop (call it B) connected via a Wireless PCI card
and a laptop directly connected. The laptop is for work and has a
different group name than the other two computers and can't be seen by
either computer A or computer B, which is expected..

Until recently, I could access computer B from computer A. Now I
can't. They both belong to group MSHOME. Computer B has no problem
sharing the internet connection, but if I ping computer A from it, I
get no response. WEP is enabled and I checked the encryption and it
looks correct on both ends. Boith are enabled, 64-bit, with the same
encryption key. If I check the DHCP clients table, computer A shows up
and so does the laptop, but not computer B. Also, I cannot ping
computer B from computer A.

I can't think what else to check. I can't think of what I could have
done to change the network configuration. I'm at wits end. What am I
missing?

If you cannot ping between computer A and B there is a layer 3 or lower
problem. Double check the WEP mode and key including the key ID I think
there's 4 to choose from for 64bit. Check the router doesn't have access
control set up if so ensure the MAC address of computer B is there.

You must find the problem at layers 2 or 3 before you try and play with the
upper layers that windows uses.

Check the subnet mask of the machines to ensure they are both on the same
network.

 

[CWatters]

If you cannot ping between computer A and B there is a layer 3 or lower
problem. Double check the WEP mode and key including the key ID I think
there's 4 to choose from for 64bit. Check the router doesn't have access
control set up if so ensure the MAC address of computer B is there.

I don't think this can be his problem because he said...

Computer B has no problem sharing the internet connection.

Doesn't this imply his wireless link to the router is working OK?

But then he says..

If I check the DHCP clients table, computer A shows up
and so does the laptop, but not computer B. Also, I cannot ping
computer B from computer A.

So how can B be connecting to the Internet if it isn't getting an IP address
from the router/DHCP?

It all seems a bit inconsistent, or have I missed something?

 

[Lenny Toulson]

I can't think what else to check. I can't think of what I could have
done to change the network configuration. I'm at wits end. What am I
missing?

Confirm that my understanding is correct: Both A and B can surf the 'Net at
the same time with no difficulties. However, neither has knowledge of each
other.

If that is correct, are you sure that B is actually using your router to
access the 'Net? You said that the DHCP client table for your router is not
showing B, but B can surf the net. The likely causes of this are: 1) B has
a static IP address or 2) B is on a different router. If B has connected to
a neighboring access point, it would be on a separate network and wouldn't
be able to ping any of your PCs.

Use the wireless network configuration tool to verify the access point in
use by your wireless card. Your configuration utility should allow you to
set the desired access point to be used. If the one in use is not yours,
set it to be yours and yours only. (Or, set it to be primarily yours, then
use the other one as backup for when yours is out.

If you are indeed on another access point, take this as an object lesson in
why you should secure your own wireless network. If you do not wish to
allow unfettered access to your LAN and/or Internet connection, take this
opportunity to review your security settings.

I recommend the following:
1. Disable DHCP or at least restrict the pool of IP addresses to the
specific number of PCs on your LAN.
2. Disable SSID broadcast on your access point.
3. Enable MAC address filtering using the MAC addresses of your PCs' NICs.
4. Enable encryption (WEP, but WPA is better, if available for your
devices).

These steps should be sufficient to protect most home networks from all but
very determined hackers.

And if your neighbor has an open network, why would they bother with
yours...?

 

[Sandy]

the same time with no difficulties. However, neither has knowledge of each
other.

That is correct. Both computers can surf the net, but have no
knowledge of each other. I don't know if it matters, since as a
previous poster suggested, my problems may be below the Windows layer,
but computer A is running XP Pro and computer B is running Windows 98.

If that is correct, are you sure that B is actually using your router to
access the 'Net? You said that the DHCP client table for your router is not
showing B, but B can surf the net. The likely causes of this are: 1) B has
a static IP address or 2) B is on a different router. If B has connected to
a neighboring access point, it would be on a separate network and wouldn't
be able to ping any of your PCs.

It has to be using the router. There is no other access to the
internet. I checked the network config andit is using Dynamic IP
addressing.

Use the wireless network configuration tool to verify the access point in
use by your wireless card. Your configuration utility should allow you to
set the desired access point to be used. If the one in use is not yours,
set it to be yours and yours only. (Or, set it to be primarily yours, then
use the other one as backup for when yours is out.

Okay, now you lost me. How do I determine the access point?

 

[wk]

From each computer browse to http://checkip.dyndns.org/

Do both of them show the same IP address? If they do then both are
connected through your router. If not, one of them is connected
through somebody else's wireless network.

wk

 

[Sandy]

network.

Okay, that may be the problem. the subnet mask of computer A is
255.255.255.0. The subnet mask of computer B is 255.0.0.0. How to I
fix this?

 

[Paul Landregan]

Okay, that may be the problem. the subnet mask of computer A is
255.255.255.0. The subnet mask of computer B is 255.0.0.0. How to I
fix this?

If this has been DHCP set then your looking at two different
routers/wireless networks. Are the actual IP's similar eg 192.168.1.1 and
192.168.1.2 or totally different eg 192.168.1.1 and 10.1.1.1.

If the subnet mask is set manually then right click in network neighbourhood
to get to network properties, goto TCP/IP properties and enter the correct
Subnet mask

 

[Paul Landregan]

Okay, that may be the problem. the subnet mask of computer A is
255.255.255.0. The subnet mask of computer B is 255.0.0.0. How to I
fix this?

Also try this on each computer, go to a command prompt. Start, Run then type
Cmd.

Type Ipconfig /all this will reveal all the IP information you need
including the ip address of the serving DCHP server. if they are different
thn you have a problem, your latched to somebody else's network.

 

[Sandy]

If this has been DHCP set then your looking at two different
routers/wireless networks. Are the actual IP's similar eg 192.168.1.1 and
192.168.1.2 or totally different eg 192.168.1.1 and 10.1.1.1.

Nope, the IPs are the same 192.168.1.1

If the subnet mask is set manually then right click in network neighbourhood
to get to network properties, goto TCP/IP properties and enter the correct
Subnet mask

The IPs are assigned dynamically, so I can't change the subnet mask.

 

[Sandy]

Also try this on each computer, go to a command prompt. Start, Run then type
Cmd.

Type Ipconfig /all this will reveal all the IP information you need
including the ip address of the serving DCHP server. if they are different
thn you have a problem, your latched to somebody else's network.

Okay. I ran winipcfg on the computer I couldn't see and did a RENEW
ALL. This reset the subnet mask to 255.255.255.0. Now if I go back
down to computer A I can see computer B in the DHCP clients table.

I still can't ping computer B and if I try to explore MSHOME on
computer A, it's not accessible. I wonder if part of the problem is
that on computer B, I have four TCP/IP adapters defined:

1) AOL Adapter
2) AOL DIal up adapter
3) PPP adapter
4) Wireless PCI adapter

Not knowing enough, I'm afraid to delete anything without knowing the
consequences, but the subnet mask for the AOL adapter is 255.255.0.0
while the subnet mask for the PCI adapter is 255.255.255.0. COuld
this be causing a conflict?

 

[Paul Landregan]

Nope, the IPs are the same 192.168.1.1


The IPs are assigned dynamically, so I can't change the subnet mask.

If the 2 IP's of the 2 machines are the same this would explain why they
cant talk to each other.
The IP's must be different but on the same subnet. so 192.168.1.1 and
192.168.1.2 is fine. DCHP should have done this, not give them both the same
address.

 

[Sandy]

This may be due to still having the same IP address - something that DHCP
should have prevented. Are you *sure* you're not seeing somebody else's
net?

Maybe I wasn't clear. The two computers are getting assigned
different IP addresses. 198.162.1.100 and 198.162.1.101

 

[Sandy]

My fault I realized where I created the confusion. When you used the
example of 198.162.1.1 I confused the DHCP server (which is
198.162.1.1) with the IP address. As I replied, the IP addresses are
in deed unique.

 

[Lenny Toulson]

Okay. I ran winipcfg on the computer I couldn't see and did a RENEW
ALL. This reset the subnet mask to 255.255.255.0. Now if I go back
down to computer A I can see computer B in the DHCP clients table.

Subnet mask is only part of the issue. When you ran "renew", did you get a
new IP address along with the new subnet mask?

I still can't ping computer B and if I try to explore MSHOME on
computer A, it's not accessible. I wonder if part of the problem is
that on computer B, I have four TCP/IP adapters defined:

This may be due to still having the same IP address - something that DHCP
should have prevented. Are you *sure* you're not seeing somebody else's
net?

1) AOL Adapter
2) AOL DIal up adapter
3) PPP adapter
4) Wireless PCI adapter

Not knowing enough, I'm afraid to delete anything without knowing the
consequences, but the subnet mask for the AOL adapter is 255.255.0.0
while the subnet mask for the PCI adapter is 255.255.255.0. COuld
this be causing a conflict?

I doubt this is an issue. Each of these is bound to a specific adapter and
you should be using only the "Wireless PCI" adapter for your LAN.

Of course, with AOhell...

 

[Bob Johns]

From each computer browse to http://checkip.dyndns.org/

Do both of them show the same IP address? If they do then both are
connected through your router. If not, one of them is connected
through somebody else's wireless network.

wk

Getting into this late but there are no firewalls, right? If there is this
could be the reason the boxes can't see each other.

Bob J.
Guam U.S.A.

 

[Lenny Toulson]

Maybe I wasn't clear. The two computers are getting assigned
different IP addresses. 198.162.1.100 and 198.162.1.101

Well, this is looking much less like a wireless networking issue.

I have had problems on one client's "mixed" network running XP and Win98.
However, in that situation all PCs could ping each other, but not browse
shares in Windows Explorer. I finally had to convince them to upgrade to
WinXP to resolve the issue.

Searching groups.google.com will reveal that I wasn't even close to being
alone in having networking issues on XP/98 LANs. I fear you will not be the
last. One of the troubleshooting steps recommended for that situation
included removing the NetBEUI protocol from all machines (it's not supported
on XP). Another recommendation was to force its installation on XP (that
didn't help at all in my situation).

I tried a lot of things I found in perusing the archives. Nothing worked -
until they upgraded to XP and everything has worked smoothly ever since.

Is that out of the question for you?

 

[Sandy]

Well, this is looking much less like a wireless networking issue.

I agree since I can use the interenet and see the machine on the DHCP
clients list. After this I'll continue the discussion on
microsoft.public.windowsxp.basics only.

Searching groups.google.com will reveal that I wasn't even close to being
alone in having networking issues on XP/98 LANs. I fear you will not be the
last. One of the troubleshooting steps recommended for that situation
included removing the NetBEUI protocol from all machines (it's not supported
on XP). Another recommendation was to force its installation on XP (that
didn't help at all in my situation).

I'll try removing the NetBEUI and see what happens. What I still
can't understand is why it worked at one time and now doesn't. When
that happens, I try to figure out what changed, since it's the most
logical thing to look at.

I tried a lot of things I found in perusing the archives. Nothing worked -
until they upgraded to XP and everything has worked smoothly ever since.

Is that out of the question for you?

Yes, as much as I'd like to, it has a 20 gig drive that would have
problems with the change to the boot sector location.

 

[Sandy]

Getting into this late but there are no firewalls, right? If there is this
could be the reason the boxes can't see each other.

Bob J.
Guam U.S.A.

I'm running Norton Internet Security.

New information I just discovered. The laptop can see computer B,
which makes me believe the problem is on the main computer, since it
can't see either computer B or the laptop. As a matter of fact, I
just learned something, I didn't realize that once I disconnected from
VPN, I would be able to "join" the home network. That solves some
minor problems for me, like being able to use my printer.

But I don't want to confuse the issue here. The main question is,
why can the laptop see one computer and not the main computer and why
can't the main computer see the other two. And computer B can see the
laptop. The odd man out seems to be the main computer.

 

[Paul Shirley]

I have had problems on one client's "mixed" network running XP and
Win98. However, in that situation all PCs could ping each other, but
not browse shares in Windows Explorer. I finally had to convince them
to upgrade to WinXP to resolve the issue.

Using WinXP's firewall caused similar problems on my mixed network.