Unidentified Network

[karldenton]

Suddenly getting computers loose connection and say "No internet". If you unplug the network cable and plug it back in you get "Unidentified network". Occurring randomly on different machines

 

Any ideas please? Thanks

[karldenton]

PS - no errors in DNS / DHCP

[Mark182]

Have you run out of IP addresses? What does IP config look like on a client?

[ITJS2015]

Sounds like a loop cable issue into a switch or from 2 sockets in a classroom

[karldenton]

Have you run out of IP addresses? What does IP config look like on a client?

 

Plenty of IP addresses left on DHCP. An Ipconfig shows a 169 address.

 

I moved one into a different network wall socket and it works fine. The main computer in the ICT suite did it but it came back online after 30 minutes or so

[stevewill6]

I have had this problem recently with 2 computers.

 

Swapping the port on the switch solved it for me until i could restart the switch.

[Sagima]

I get this on 1 server when it reboots - otherwise not seen on my network. unplugging and plugging the ethernet cable resolves it.

It's happened on multiple switches (I think that server has been through 4) so I've always assumed it was a firmware thing. It's being replaced in half term so I may never find out.

 

My first thought with yours is that if it's different machines and at random (on different switches) that somewhere spanning tree configuration has changed or something else that causes the dhcp request to timeout

[pantscat]

Are all computers on the same switch?

 

If not - do you have spanning-tree enabled?

[karldenton]

Had this again on some machines today. Can't ping a DC when it happens. It gets a 169 address. Can't ping DC IP address either or any other servers. Restart doesn't fix it.

 

Switches are netgear

 

Any ideas?

[Sagima]

Had this again on some machines today. Can't ping a DC when it happens. It gets a 169 address. Can't ping DC IP address either or any other servers. Restart doesn't fix it.

 

Switches are netgear

 

Any ideas?

 

can you do an ipconfig /release & ipconfig /renew and get an ip?

[SHimmer45]

169 address suggests that the machine has self assigned an IP (usually) because it hasn't received an IP address from DHCP.

also believe if a machine cant ping its gateway it will produce similar behavior

[karldenton]

Rebooted the switch - still the same

[karldenton]

Computer not showing in DHCP leases, despite it working this morning. No DHCP errors in event viewer

[Sagima]

Are there dhcp addresses free to issue?

[karldenton]

Are there dhcp addresses free to issue?

 

Yeah 54 spare

[SHimmer45]

do you have any mac filter in place?

 

or go right back and check the cable and point for damage

[karldenton]

No mac filter, and they are plugged into different points. There are 4 machines in a room doing it, 2 are seperate the other 2 are plugged into a mini switch, but there is another one on that switch working fine.

[Sagima]

Are you absolutely sure you don't have spanning tree enabled - it really seems like the sort of thing that happens when it isn't set up properly.

[karldenton]

Are you absolutely sure you don't have spanning tree enabled - it really seems like the sort of thing that happens when it isn't set up properly.

 

Just checked on all the switches - its definitely disabled

 

[Sagima]

Is your DHCP server virtual?

[Davit2005]

Do you have multiple vLANs or Subnets??

 

The 169 address indicates that it cannot contact a DHCP server and is using an APIPA address assigned by the local machine as a fallback. Sure kids aren't mucking about with cables :-) .

 

I'd also check cables as had an issue like that once when trying to PXE boot and another exact issue with a cheapo switch when clients would not get DHCP addresses.

[MatthewL]

Have you tested your network point from panel to socket, could be a fault cable.

[pantscat]

Have you tried restarting the DHCP service? Anything in event viewer on the server?