Ping stops responding.

[Control Freq]

Hi,
I know that ping failures is a frequent problem, and there is alot of
info available on how to troubleshoot this type of problem, but my
problem is subtley different from most.

I have two computers, (A) is an XP Pro Laptop, (B) is a Windows 2000
Server Desktop.

Both have static IP Address, (A) 192.168.1.10 and (B) is 192.168.1.11
Both have subnet masks of 255.255.255.0

(B) and (A) are networked together through a 3Com Hub. These are the
only two machines on the network. Quite simple.

Anyway, to the problem:

1) (B) cannot ping (A). At all.
2) (A) CAN ping (B), but after a few minutes the ping responses stop
with 'request timed out'.

There is no firewall running on either machine. I know that is bd
practice, but I am trying to solve this intermittent connection
problem.

So, what could be causing ping packets to be blocked from (B) to (A),
and what could cause pings from (A) to (B) to run for a while, before
getting 'request timed out'.

Any suggestions appreciated.

Regards

 

[Lem]

Hi,
I know that ping failures is a frequent problem, and there is alot of
info available on how to troubleshoot this type of problem, but my
problem is subtley different from most.

I have two computers, (A) is an XP Pro Laptop, (B) is a Windows 2000
Server Desktop.

Both have static IP Address, (A) 192.168.1.10 and (B) is 192.168.1.11
Both have subnet masks of 255.255.255.0

(B) and (A) are networked together through a 3Com Hub. These are the
only two machines on the network. Quite simple.

Anyway, to the problem:

1) (B) cannot ping (A). At all.
2) (A) CAN ping (B), but after a few minutes the ping responses stop
with 'request timed out'.

There is no firewall running on either machine. I know that is bd
practice, but I am trying to solve this intermittent connection
problem.

So, what could be causing ping packets to be blocked from (B) to (A),
and what could cause pings from (A) to (B) to run for a while, before
getting 'request timed out'.

Any suggestions appreciated.

Regards

Bad hub?

Check Task Manager on both computers, particularly A, to identify
everything that's running. You may have a firewall (or an antivirus
application behaving like a firewall). Also note that Nvidia network
adapters (either PCI or motherboard) may include a firewall that you're
not aware of:
http://networking.nitecruzr.net/2006/02/hidden-personal-firewall-nvidia-nforce.html

--
Lem -- MS-MVP

To the moon and back with 2K words of RAM and 36K words of ROM.
http://en.wikipedia.org/wiki/Apollo_Guidance_Computer
http://history.nasa.gov/afj/compessay.htm

 

[AJR]

Regarding "... (A) CAN ping (B...." - not true - B is not responding.

Couple of thoughts - TCP port 445 must be opened - ICMP setting "Allow
incoming echo requests" must be checked.

Also you do not state whether or not the network functions OK and regarding
" I am trying to solve this intermittent connection..." - how are you
applying "intermittent".

 

[Jack \(MVP-Networking\).]

Hi
Are these two computers connected to the Internet (if yes how)?
Jack (MVP-Networking).

 

[Control Freq]

Wow, some great responses thanks.

To address the points made by all respondents:

1) I have tried another HUB, and also replced it with a cheap Pluscom
switch. Still getting the same problems, so I think that rules out the
hub/switch.
I also replaced all CAT 5 cables, still no joy.

2) I checked firewalls. The XP Pro Laptop has the firewall switched
off, for the purposes of this test.
I cannot find a firewall icon on the Windows 200 Server Control Panel.
And I don't think that a third party firewall was installed. But I
will check this.

3) Firewall in the network card. I have never heard of this, but it is
worth investigating. The network card in the server is an Intel ProSet
III. I will check.

4) These computers are not connected to internet. Just a small local
network. There is just these two computers, and a hub/switch. Thats
it.


The problem I am seeing is an intermittent loss of ping responses.

Problems
1) (B) (Win 2K Server) cannot ping (A) (XP Pro Laptop) at all.
2) (A) can ping (B) some of the time.
On (A) I start a ping command like 'ping -t 192.168.1.11' and leave
that running.
I now see regular good responses from (B). So far so good.

Now, I make a cup of coffee, and keep watching the ping responses.
After a while (maybe 10 to 15 minutes) the ping responses will get
'request timed out'.
There is nothing else I am doing (other than drinking my coffee).
I will see a few minutes of 'request timed out'.
I continue to stand there, scratching my head, and all of a sudden,
the good ping responses might come back.

This is definately weird. After a few more minutes, the ping responses
will go back to 'request timed out' and then if I leave it running a
while longer, they might turn back into good responses.

I defaintely need some help here. It's as if the system is haunted.


Any more ideas?

 

[Control Freq]

Well, I fixed the problem. I don't often get to respond to my own
questions.

The problem was caused by a corrupt ARP cache. I write down the MAC
and IP addresses shown using 'arp -a'.
After exactly ten minutes the OS will refresh the list.

I do an 'arp -a' again and notice that some of the MAC addresses are
appearing in the list twice! to different IP addresses.
I don't know what is causing this. But, adding static ARP entries
using 'arp -s ....' fixes the problem for me. Fortunately, my network
uses static IP addresses so this is an easy and permanaent fix.

But, the question still remains about what is causing the ARP cache
corruption?

Regards

 

[Charliec]

I having a bit of the same problem - the ping has stop working between
my desktop and laptop which are on a home network 4-Port Router
(desktop has WinXP and laptop has Vista). I share the desktop's "E"
drive with the laptop. As of a few days ago, the two pcs are not
seeing each other on the network.

What is the ARP cache and how does one access it?

Thanks

Well, I fixed the problem. I don't often get to respond to my own
questions.

The problem was caused by a corrupt ARP cache. I write down the MAC
and IP addresses shown using 'arp -a'.
After exactly ten minutes the OS will refresh the list.

I do an 'arp -a' again and notice that some of the MAC addresses are
appearing in the list twice! to different IP addresses.
I don't know what is causing this. But, adding static ARP entries
using 'arp -s ....' fixes the problem for me. Fortunately, my network
uses static IP addresses so this is an easy and permanaent fix.

But, the question still remains about what is causing the ARP cache
corruption?

Regards

******************************************************
Charliec

 

[Control Freq]

Hi,

The ARP cache (Address Resolution Protocol) is a list of IP addresses
and matching MAC addresses. Each network device has a MAC address. The
MAC address is fixed, and should be unique in the world. The IP
address is assigned, either statically, or dynamically by a local DHCP
server.

So, each computer on a network keeps an ARP cache.

You can use the 'arp' command from a windows command prompt. Just type
'arp -a' (without the quotes) to see the current list.

The is plenty of help on google about this.


Best of luck.