Peculiar Yet Critical Network Problem

[Guest]

Windows 2003 Server, Windows XP. I have a very peculiar problem. All the
systems in my network, except two, can access (ping) two of my network
printers. I have a new Dell server and a desktop station that cannot ping
these two printers. The server and desktop can ping every other addresses
and
printer, just not these two. It is not the switch I am plugged into, as I
have tried my laptop on the same ports and can ping everything. What might
be causing this problem of two systems not being able to ping just two
addresses, when everyone else can ping these addresses?

P.S. I ran into this problem as I was trying to connect my network printers
to my new server. Two of my four printers connected just fine, but two did
not. That is when I tried the ping and found it did not work for the two
printers. Help!

 

[Ron Lowe]

Windows 2003 Server, Windows XP. I have a very peculiar problem. All the
systems in my network, except two, can access (ping) two of my network
printers. I have a new Dell server and a desktop station that cannot ping
these two printers. The server and desktop can ping every other addresses
and
printer, just not these two. It is not the switch I am plugged into, as I
have tried my laptop on the same ports and can ping everything. What
might
be causing this problem of two systems not being able to ping just two
addresses, when everyone else can ping these addresses?

P.S. I ran into this problem as I was trying to connect my network
printers
to my new server. Two of my four printers connected just fine, but two
did
not. That is when I tried the ping and found it did not work for the two
printers. Help!

Sounds like an odd IP routing problem, or a firewall issue.

So:
All other machines except the problem ones can ping these printers;
The problem ones can ping all other machines.
Is that correct?

First off, disable any firewalls on the machines as a troubleshooting
measure.
Does that help?

Assuming we have fallen through to an IP routing issue, then the answer lies
in details, details.
To ping a target machine, there must be a route to the target, and a return
route from the target.
For example, it's possible that the 2 problem machines have IP addresses
that are off-subnet as far as the printer is concerned, because the
printer's subnet mask is wrong. It's also possible that the printer's IP
address is off-subnet as far as the problem machines are concerned. So we
need to gather some information.

We need several pieces of information.

1) What exact error does the ping return? Timeout or unreachable?

2) Is the target printer on the same local subnet, or is located on a remote
subnet accessed via some sort of router?

3) On the printer configuration, what is the IP address, subnet mask and
Default Gateway?

4) What is the IP address, subnet mask and Default Gateway on the problem
PC?

5) What is the IP address, subnet mask and Default Gateway on a working PC?

6) On the printer configuration, what is the IP address, subnet mask and
Default Gateway?

 

[Guest]

Sounds like an odd IP routing problem, or a firewall issue.

So:
All other machines except the problem ones can ping these printers;
The problem ones can ping all other machines.
Is that correct?

First off, disable any firewalls on the machines as a troubleshooting
measure.
Does that help?

Assuming we have fallen through to an IP routing issue, then the answer lies
in details, details.
To ping a target machine, there must be a route to the target, and a return
route from the target.
For example, it's possible that the 2 problem machines have IP addresses
that are off-subnet as far as the printer is concerned, because the
printer's subnet mask is wrong. It's also possible that the printer's IP
address is off-subnet as far as the problem machines are concerned. So we
need to gather some information.

We need several pieces of information.

1) What exact error does the ping return? Timeout or unreachable?

The error is a Timeout

2) Is the target printer on the same local subnet, or is located on a remote
subnet accessed via some sort of router?

The target printer is on the same local subnet.

3) On the printer configuration, what is the IP address, subnet mask and
Default Gateway?

IP: 10.251.0.37

Subnet Mask: 255.255.255.224
(Which is different than the 255.255.255.0 used on the other LaserJet 8100.
However, both LaserJets have been accessible with this configuration from our
old server and all workstations)

Gateway: 10.251.0.33

4) What is the IP address, subnet mask and Default Gateway on the problem
PC?

IP: 10.251.0.64 (Also 10.251.0.1 our server does not ping the printer either)
Subnet Mask: 255.255.255.0
Default Gateway: 10.251.0.254

5) What is the IP address, subnet mask and Default Gateway on a working PC?

IP: 10.251.0.60
Subnet Make: 255.255.255.0
Default Gateway: 10.251.0.254

 

[Ron Lowe]

1) What exact error does the ping return? Timeout or unreachable?

The error is a Timeout


The target printer is on the same local subnet.


IP: 10.251.0.37

Subnet Mask: 255.255.255.224
(Which is different than the 255.255.255.0 used on the other LaserJet
8100.
However, both LaserJets have been accessible with this configuration from
our
old server and all workstations)

Gateway: 10.251.0.33


IP: 10.251.0.64 (Also 10.251.0.1 our server does not ping the printer
either)
Subnet Mask: 255.255.255.0
Default Gateway: 10.251.0.254


IP: 10.251.0.60
Subnet Make: 255.255.255.0
Default Gateway: 10.251.0.254

Well,there's your problem.
The printer's subnet mask is wrong.

With an IP address of 10.251.0.37 and a mask of 255.255.255.240,
that puts the printer in a subnet with this range of IP addresses:

10.251.0.32 - 10.251.0.63.

The addresses 10.251.0.64 and 10.251.0.1 are off-subnet as far as the
printer is concerned. When it tries to respond to the pings, it is routing
the packets to it's default gateway ( .33, probably a non-existent gateway )
rather than ARPing them on the local subnet. The replies are getting
mis-routed.

The working machine ( 10.251.0.60 ) is within the printer's subnet, and so
it works.

Change the subnet mask on the printer to 255.255.255.0

 

[Ron Lowe]

With an IP address of 10.251.0.37 and a mask of 255.255.255.240,

^^^
Obviously, I meant .224!
Typo on my part there.

The caclulations are correct!

 

[Guest]

THANKS ROB!

The problem appears to have been that the two printers in question had a
different subnet mask (255.255.255.224) than the rest of the net
(255.255.255.0). When I reconfigurred the printers (an HP 8100N and Lexmark
Optra L) to the proper subnet mask, then I was able to access the printers
from all systems. What baffles me, but for now is moot, is why only two out
of our twenty systems had a problem accessing the printers.

Lesson learned:

When you place a new server on your net, and you want to make the new server
the print server, make sure that your printers are configured with the right
subnet mask and that the printers have their default gateway set to the new
server's IP address.

 

[Ron Lowe]

THANKS ROB!

You're welcome.

What baffles me, but for now is moot, is why only two out
of our twenty systems had a problem accessing the printers.

Pure chance on the IP addresses.
Only 2 machines had IP addresses outwith the range 10.251.0.32 -
10.251.0.63.
All the others must have been within that range.

 

[Ron Lowe]

and that the printers have their default gateway set to the new

server's IP address.

Incidentally, the Default Gateway does not need to point to the print
server.
It should point to the router that routes traffic off your LAN to other
subnets.

If there is no such thing, then you don't need to specify a Default Gateway,
since everything is local to your LAN.

In that case, all you need is the IP address and subnet mask.