Intermittent network behaviour

We have an intermittent problem that started (approximately) when we installed a VPN between our 2 offices.

Office 1 has an XP server, and 5 PCs with win XP, 2000 and 98. Office 2 has 2 Win XP PCs. The connection between the 2 uses Netgear FVS318 firewall/routers and D-Link 302G ADSL modems.

A day or so before the change to VPN 1 PC crashed several times, including blue-screen-of-death messages. The real problem started somewhat later, after the installation of the VPN. The network connections within office 1 have become extremely intermittent. Office 2 is largely unaffected.

Sometimes the entire network disappears for one or more PCs, and somewhat later, without making any changes, it reappears again. At other times individual PCs disappear from the network.

Her is an example. One PC shares its disk with another. This share disappeared. In order to keep working, the user set up a new share for just the folder that was required. This share was visible for an hour or so, when it too disappeared. While we were scratching our heads, the entire disk suddenly became shared again.

At other times people will use all or part of the internet connection. For example, while able to receive and send email, web browsing may be impossible. Sometimes just the link between the 2 offices disappears while the local network stays up (i.e. only the local network is visible in My Network Places), at other times the reverse happens.

At the same time, the office 2 people have no problems with their internal network, nor with internet access. To them the office 1 network is also always visible, although the connection can become very slow.

Our virus software is fully up-to-date (it even catches Mydoom) and most PCs as well as the server have been scanned. We have tried unplugging the router but that made no change at all. At one stage we unplugged 3 IP printers, and found that the network came up immediately, but only for half an hour or so. We tried changing IP settings on the PCs and server, to no avail.

Any ideas that can help us resolve this problem will be most appreciated

how is the vpn done... on the router or through a connection on the client pc? Usually if a device is participating in a vpn tunnel then all other network devices are disabled or locked down.

For example. When I connected to my company's vpn from my home pc I can no longer access my lan at home nor can print to my network printer. This is to ensure rogue devices cannot access the private network.

The fact that you unplugged the router and still experienced problems leads me to believe it is a browser master issue with Windows. I fought this problem a ton with Win98. 2k and XP should be better though, but the 98 box maybe creating the conflicts.

The VPN is done through the router.

And it's not only the local LAN that suffers. The remote LAN can also disappear.

Yesterday we thought we had the solution: one guy was still connecting via a USB ADSL modem (a remnant from before we installed the router and VPN). When we disabled that connection, the network was stable for most of the day. Unfortunately, late in the afternoon the entire network suddenly went down for everyone. No PC could see anything on the local network. Email also stopped working as well as internet browsing. Yet I was still able to ping urls across the world...

I have switched off everything (PCs, router, server, modem, the lot - fortunately it's a small office) for the weekend.

I have had this problem running Wingate VPN, it was a problem with Master browser elections and was resolved by disabling computer browser in services for all but the server/clients, also in the registry i forced "IsDomainManager" to "TRUE". This forces the server to always be master browser and hold the list of network resources whilst the VPN is active, another problem can be Radio NICS as if one of these is elected BM and radio contact becomes twitchy, the list cannot be accessed.

Regards

JonO

If you need further help you can mail me or contact thru our VPN self help group http://fishyfingerssl.com/phpBB2/vi...9c2bcb3dbeb9a54

You did not mention whether IP still worked or not, when the network goes down can you ping from one PC to another PC on the same network or is it just a netbios issue where you cant browse through network neighborhood. My point is I have seen switches go bad and cause this same problem where there is random packet loss at times and no packet loss at other times and nothing in the log of the switch. If it is just netbios as the issue then the election issue may be your problem as stated above.

I thought I replied to this yesterday, but I can't see my reply. So here goes it again.

The problem was caused by XP being to smart for its own good. 2 PCs running XP have motherboards with on-board NICs. When XP was installed, it recognised the network chip and installed drivers for it, so everything looked and worked fine. However, what XP did not find was the mac addresses for the NICs, leaving them set at all-0's.

This worked fine, without a hiccup, until the router was installed, and then the problems started.

When I discovered the missing mac addresses I ran the installer on the motherboard's CD, and bingo, there's the correct address, and a working network.

I've decided not to spend any time on discovering why it worked without the router...

That made no sense at all hehehe!