Resolved Inconsistent LAN connectivity

Something rather strange seems to happen to my LAN under certain circumstances

The current set up is with four computers,
A, (vista); B, (Win 7); C, (Win 7); D, (Win XP).

Usually they are powered on in that same order and there is complete interconnectivity between all of them with no issues at all.


However, if I only power on B and C, then something odd appears to happen.

B can see C and access files with no problem.

However, C cannot see B which is not shown when clicking on Windows Explorer ... Networks. But, and this is where I admit to being confused, if I access the full network map I can see that both B and C are recognised and the on-screen graphics show them connected, via a switch and a gateway, to the Internet. Both computers can in fact see the Internet with no issues.


However it is not possible to access the 'missing' one on the LAN.


Not sure what the problem is other than they are both Win 7 boxes. A, B and C are using McAfee Firewall, which by default disables the Windows Firewall, and as far as I can check, the configuration seems to be identical:
Connections:
- allow access to 192.168.10 - 192.168.1.255
- Security level - Work
Ports and System Services allows:
- Microsoft Directory Server, port 445
- Windows File Sharing, ports 137 - 139
- Network Time Protocol, post 123 (although this is of course, irrelevant here)
- Common Operating Ports, port 5357
- Universal PnP ports 500, 1900, 2869 (although this is of course, irrelevant here)


Network configuration, via Network and Sharing Center ... Change Advanced Settings appear to identical:
Network discovery - on
File and printer sharing - on.
Public folder sharing - on
File sharing - 128 bit encryption - on
password protected sharing - on
Homegroup connection - on (although neither are in a homegroup because of the 'mixed' OS's on the LAN


As a further point, powering B and C and then A also results in some loss of connectivity, which seems to suggest that in some way A is acting as some form of controlling device, unlikely as that appears to be!


How is it possible that the order in which computers are powered on, or not as the case may be, can affect interconnectivity?

Utterly frustrating!

 

I believe that I have resolved the issue.

Checking deeper into the McAfee configuration, I found that the Firewall Security Level on one of the two computers that had this issue originally was set to Outgoing Access, and the other was set to Full access.


By ensuring that both are set to allow Full access the problem seems to have been cleared.

I will carry out some further checks later and post back to confirm that the issue is resolved.

Now wish I'd checked deeper rather than just checking the configurations for Connections and Ports and System Services

Can't help walking around muttering Bl**dy McAfee at the moment.

 

Point taken, Arie.

However, the problem is only partially resolved as of this moment. I am in the process of exploring an alternative solution which will take a little time. Once I have followed that through I will, as always be closing the thread properly. Thanks for your interest.

The current solution, or rather kludge is that by turning off the firewall on all computers full interconnectivity can be established; once that has happened, that is, I see the whole network on each box, I can then turn the firewall back on and I'm back in business as usual.


As I say, it's a kludge and I'm not happy at this stage. Watch this space!!

 

I believe this has now finally been resolved!

Further experimentation on the two Win 7 boxes was focused on the McAfee Connections page.

By default this was set to the default IP address range of 192.168.1.0 - 192.168.1.255, which should, at least superficially, have given full access.

Based on information gleaned from various searches several days ago I had attempted to change, or rather, edit, that setting to 192.168.1.0 - 192.168.1.254. My understanding, imperfect as it usually is, was that 255 may have been 'out of range'. This edit was not possible as McAfee flagged up an error message about illegal values. So, at that time I dropped that idea and cast around for further ideas.

Today I had the idea of adding a further rule, rather than editing an existing one, to the McAfee Connections page - 192.168.1.1 - 192.168.1.50 to both of the Win 7 boxes. (This seemed to be an ample and sufficient range for my current and foreseeable requirements.)

Hey presto!

Suddenly the Win 7 boxes could see each other without any issues.

Next, I fired up the Vista box - again success!

Finally, I fired up the old XP Pro box - more success!

Now everything seems to be functioning correctly and there appears to be no need to temporarily disable the McAfee Firewall any more

Not sure why this latest 'fix' has (at least so far) worked, but I do recall reading somewhere that it is possible that with the McAfee Firewall some default rules may not always register correctly.

It is all rather odd because the McAfee Firewall on the Vista box works perfectly well with the default IP settings. (The XP box uses different software.)


It all leads me to draw some basic conclusions.

The McAfee Firewall on Vista boxes does function correctly.

The McAfee Firewall on Win 7 boxes, where it is tightly, (and seemingly inextricably) linked to the Windows Firewall is to some extent flawed.