[Personal Alpha] No IP access to Host but ping (again)

[Didier DTL Morandi]

Good morning Jon,

> What can you do from PC1 to VMS1 (DTL01) that you can not do from PC2 to VMS2 (DTL03)?

> What can you do from VMS1 (DTL01) to PC1 that you can't do from VMS2 (DTL03) to PC2?

I can do everything dealing with TCP/IP communications between PC1 and VMS1 in both directions

I can do everything dealing with TCP/IP communications between PC1 and VMS2 in both directions

I cannot do anything between PC2 and VMS2 but
ping.

After a telnet attempt from PC2 to VMS2, network logfile sez:
2009-12-07 11:49:51 OPEN TCP 192.168.1.14 192.168.1.103 1145 23 - - - - - - - - -
2009-12-07 11:50:57 CLOSE TCP 192.168.1.14 192.168.1.103 1144 23 - - - - - - - - -

nothing else.

I will save my system disk on PC2/VMS2, then reinstall PA, then create a new VMS system disk. I come back later.

The only difference between these two configurations is to me the network interface.

If the previous operation gives the same results, I will remove my Ethernet card from PC1 and plug it in PC2 and see.

Talk to you later.
Thanks.

[Vadim Model]

I would try to disable TOE (TCP/IP Offload Engine) features on NetExtreme board, just in case ...

[Gregory Reut]

Hi Didier,

Network adapter could be a root cause, we don't know exactly how its dirver handles the MAC address change (forced when DECNET comes up). Another possible reason is the network switch. Are both of your systems connected to the same switch, or to different ones?

Before switching network adapters I would try what Vadim recommended (TOE off). Than I would copy the PA disk image from PC1 (where everything works) to PC2 (where it does not work), configure Windows networking on PC2 exactly as on PC1, boot VMS, and check the communications between Windows and VMS. If it works, we prove the network adapter is innocent, if it does not, proved guilty, and you could proceed with a replacement.

By the way in production environments sharing of the network adapters is not supported.

Best regards,
Greg
Stromasys

[Jon Pinkley]

Didier,

I think Vadim Model may have found your problem. It is at lease worth a try before moving hardware. Create a system restore point before the change; it could make reversing easier.

It seems more likely that the adapter is the issue than the switch it is plugged into, because the other PC can communicate ok, all the way "into" the VMS instance running it the virtual alpha. So it isn't obvious to me how the switch could be the problem.

Ping may work due to the small default size and the fact that ICMP isn't a TCP protocol; it is an IP protocol. Perhaps that is why it is treated differently. It would be interesting to see if larger ICMP packets fail to traverse the PC2 VMS2 path, especially ones that are larger that the MTU and must be fragmented.

First verify that you can send a max sized ping from PC1 to VMS1

PC1 > ping -l 65500 192.168.1.101 ! that's a lowercase L for payload length (windows ping size is payload size, not packet size)

If that doesn't work, see what the largest size is (try -l 1400, -l 1472 (1472 is the largest packet that can be sent without fragmenting with an MTU of 1500, the packet will be 1500 length, 20 byte ip header 8 byte ICMP header 1472 bytes of payload), 1500, 32000, etc.) My guess is that 65500 will work.

Then try pinging from PC2 to VMS2 with the max size packet that worked above.

PC2 > ping -l 192.168.1.103

I won't be surprised if that fails, but it may work. If it doesn't work, it is more evidence that the adapter isn't as transparent as the one in PC1.

Here are some links I found with Google concerning TCP offload

Several recommendations for method 2 in following Microsoft knowledgebase article 948496.

http://support.microsoft.com/kb/948496

http://www.windowsreference.com/networking/enabledisable-tcp-task-offloading-to-nic-in-windows/

http://social.technet.microsoft.com/Forums/en/winserverPN/thread/a55b795c-d171-4ef8-8a85-ca685d9b536d

http://www.google.com/url?q=http://social.technet.microsoft.com/Forums/en/winserverPN/thread/814a4a85-3f36-4fe3-826f-fedf7fa23a44&ei=0IodS_n5OovClAfn0dHyCQ&sa=X&oi=forum_cluster&resnum=4&ct=result&cd=1&ved=0CBEQrAIoADAD&usg=AFQjCNEEBJ8ZJLkbnzM5U_iZMEo4Ze5ZgQ


The following was vmware related, but it was concerning bridged mode and TOE and Broadcom (and disabling TOE fixed problem)

http://communities.vmware.com/thread/191085;jsessionid=CE0A767EE03AFFD9070C95493741ECA0

Once you discover the cause, make sure to update this and the Stromasys forum.

Good luck,

Jon

[Didier DTL Morandi]

Both tests on the two PCs give more or less same results. On PC2 I have:

Microsoft Windows XP [version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\Didier Morandi>ping -l 65500 192.168.1.103

Envoi d'une requête 'ping' sur 192.168.1.103 avec 65500 octets de données :

Réponse de 192.168.1.103 : octets=65500 temps=97 ms TTL=64
Réponse de 192.168.1.103 : octets=65500 temps=115 ms TTL=64
Réponse de 192.168.1.103 : octets=65500 temps=116 ms TTL=64
Réponse de 192.168.1.103 : octets=65500 temps=110 ms TTL=64

Statistiques Ping pour 192.168.1.103:
Paquets : envoyés = 4, reçus = 4, perdus = 0 (perte 0%),
Durée approximative des boucles en millisecondes :
Minimum = 97ms, Maximum = 116ms, Moyenne = 109ms

C:\Documents and Settings\Didier Morandi>

I do not know where can TOE be turned off. I have a look and come back.

[Jon Pinkley]

Didier,

To disable the tcp offloading, it had previously written "Several recommendations for method 2 in following Microsoft knowledgebase article 948496."

That should have been Article 8887750

method 2 posted at http://support.microsoft.com/kb/888750

Method 2
Disable TCP task offloading in the registry of the host computer. To do this, follow these steps.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 (http://support.microsoft.com/kb/322756/ ) How to back up and restore the registry in Windows

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. Click Edit, point to New, and then click DWORD Value.
4. Type DisableTaskOffload as the entry name, and then press ENTER.
5. Right-click DisableTaskOffload, and then click Modify.
6. In the Value data box, type a value of 1, and then click OK.
7. Quit Registry Editor.
8. Restart your computer.


See the referring thread at http://social.technet.microsoft.com/Forums/en/winserverPN/thread/814a4a85-3f36-4fe3-826f-fedf7fa23a44

Jon

[Didier DTL Morandi]

B I N G O

Don't try to explain to me why "it works", I'm too ashamed because of the work I gave to you all.

"The Network is the System", we used to say at DEC.

Thank you friends,

And a Merry Christmas to come !
Cheers.

[Jon Pinkley]

Didier,

Did you use method 2 posted at

http://support.microsoft.com/kb/888750

or did you use some other method to disable tcp offload?

Have you noticed any bad side effects from disabling the offload? (Perhaps the method suggested by Greg on the Stomasys forum)

Please let us know what you did in case someone else had the problem. Also please update the thread at the Sromasys PA forum.

http://forum.stromasys.com/userforum/index.php?t=msg&th=13&start=0&S=0a146afba08b0d415aae6c5683a1d971

I'll have to download and try out PA :-)

Thanks,

Jon

[Jon Pinkley]

I see that I did a poor job of editing.

I wrote:
--------------------
or did you use some other method to disable tcp offload?

Have you noticed any bad side effects from disabling the offload? (Perhaps the method suggested by Greg on the Stomasys forum)
---------------------

Which should have been

or did you use some other method to disable tcp offload? (Perhaps the method suggested by Greg on the Stomasys forum)

Have you noticed any bad side effects from disabling the offload?

---------------------

I did not intend that to suggest that Greg's method was more error prone.

Jon

[Didier DTL Morandi]

I did this :

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. Click Edit, point to New, and then click DWORD Value.
4. Type DisableTaskOffload as the entry name, and then press ENTER.
5. Right-click DisableTaskOffload, and then click Modify.
6. In the Value data box, type a value of 1, and then click OK.
7. Quit Registry Editor.
8. Restart your computer.