Network Connectivity Problem

[mickeyh080]

We currently are having problems in a classroom with 10 wired PC's which all run a specific music program namely Sibelius. For the program to run the client machines have to access the Sibelius network server as we have a 10 concurrent user licence. The problem has arisen that 3 of these machines have stopped working specifically when it comes to running this program. Now after chasing around looking at server settings for Sibelius and checking that the clients are trying to connect to the correct server it seems that we have come across a connectivity issue. The client machines cannot ping the sibelius server although they can ping all other servers and specific other client machines that I've tested. From the sibelius server I have tried pinging the 3 client machines and yet again the ping fails with no connection even though the server does get a reply from the other machines and other servers. We are operating on one subnet and the default VLAN for these machines. Routing is via a switch in the music room cabinet and then via the main switch back to the server room. The clients are all running Windows 7 enterprise version with no internal firewalls and the sibelius server is running 2008 R2. Slightly puzzled as have tried the usual of rebooting all clients and pinging IP addresses as opposed to their DNS names and also flushing DNS from the clients and server, no change and now slightly puzzled. Any thoughts would be welcome.

[sted]

if you swap the nic lead on a working one on a non working one what happens maybe its duff switch ports/cabling

[mickeyh080]

As the 3 client machines can ping other servers I discounted cabling or nics.

[twin--turbo]

what type of switches?

 

Dum/Smart/managed?

 

if Dum , give them a restart

 

if smart/managed clear the mac tables.

 

Rob

[mickeyh080]

All HP procurve managed switches already restarted them with no joy. Will investigate the mac tables.

[cpjitservices]

Sounds like a firewall issue somewhere ? Have you opened ports on the server and clients ? or temporary disable it see if it makes a difference.

 

Also it maybe worth running Wireshark · Download to see whats happening.

[DSapseid]

I had this exact issue with servers/clients not responding to pings. I put an allow on the firewall for file and print sharing and it started to ping both ways.

[mickeyh080]

As part of the diagnosis I have connected a new device to the network point of one of the client machines and pinged the sibelius server, this works fine. Luckily the music room machines are all in one desktops with built in wifi, I therefore have enabled the previous disabled wifi adaptor and when connected it pings to the server also. I have confirmed that no Firewalls are active and therefore think this is somehow linked to the MAC address of the client network adaptors on these 3 machines. If this is the case could the switches which route the traffic from client to server be blocking traffic specifically for these MAC addresses, i.e does Spanning Tree protocol have the means to block traffic ? My switch knowledge is limited so any thoughts again welcome.

[cpjitservices]

No Spanning-Tree will only block a link when it detects a switch loop. Have you checked the IP's of the adapters make sure they get assigned the right IP...you mentioned VLANS - is the VLAN between the server and clients being trunked properly ? and can other devices on the VLAN ping the server ? and also are the clients on the correct VLAN ? are the correct ports assigned to the VLAN it might be that a few ports arn't in the correct VLAN on the switch.

[mickeyh080]

Tried a firmware update on the music cabinet switch which connects to the network points used by these 3 client machines, no change. The IP's are correct as is the VLAN settings confirmed by using the same network port with a different device and the server can be pinged. Tried swapping the connection at the switch to an alternative port on another switch in same cabinet and get same problem. Getting very confused but wondering if the issue is with another switch in the routing back to the server blocking the MAC addresses for these 3 client machines, just a thought but not sure how to prove it ?

[Michael]

If you configure a static IP on a problematic workstation does it connect? I'd also recommend updating the NIC drivers on the workstation. This also can make all the difference.

[mickeyh080]

If you configure a static IP on a problematic workstation does it connect? I'd also recommend updating the NIC drivers on the workstation. This also can make all the difference.

 

Michael thanks for the reply I wouldnt mind trying to understand your train of thought on this one as your right in that setting a static IP results in the client being able to ping all servers no problem and then if I revert it back to DHCP it yet again fails to connect to one of the servers. I've also updated the NIC driver to the latest available from the website. In the short term applying fixed IP's to the 3 troublesome machines will keep the Music department happy but a permanent solution using DHCP would be preferable.

[twin--turbo]

Michael thanks for the reply I wouldnt mind trying to understand your train of thought on this one as your right in that setting a static IP results in the client being able to ping all servers no problem and then if I revert it back to DHCP it yet again fails to connect to one of the servers. I've also updated the NIC driver to the latest available from the website. In the short term applying fixed IP's to the 3 troublesome machines will keep the Music department happy but a permanent solution using DHCP would be preferable.

 

Does it always get the same DHCP IP?

 

If so then reserve that under a different dummy MAC to force it to get a different one.

 

Rob

[Michael]

Michael thanks for the reply I wouldnt mind trying to understand your train of thought on this one as your right in that setting a static IP results in the client being able to ping all servers no problem and then if I revert it back to DHCP it yet again fails to connect to one of the servers. I've also updated the NIC driver to the latest available from the website. In the short term applying fixed IP's to the 3 troublesome machines will keep the Music department happy but a permanent solution using DHCP would be preferable.

 

The purpose of setting a static IP confirms that the NIC is working OK, the driver's working OK and that your network switch is also working OK.

 

Reset the PC back to DHCP, allow it to obtain an IP then run ipconfig /flushdns then ipconfig /registerdns

 

Check DNS Server that your workstation has registered, then reboot.

[mickeyh080]

Thanks Michael

 

By allowing these 3 computers to be allocated a new IP address they work as advertised. Still not sure why the IP addresses previously were causing this issue as they are in the required scope and are not allocated or showing as duplicates. But its working now so has removed the problem. I will note this for future use as no doubt it will reoccur.

[psydii]

I've seen this behaviour before... and when I have managed to get to the bottom of it, the problem usually turns out to be that two machines have the same IP. I most often encounter it when Mac's reappear on the network having been asleep for longer than their lease lifetime.