IP address but no network access

[bert113]

Hello.. could really do with some advice/help as I'm stuck to be honest...

I have a number of PC's that obtain an IP address but then can't access any network drives or the internet, they can ping anything on their own vlan but nothing outside it.

 

It happens randomly and with out any pattern but only on 2 of the 6 vlans. I can't see any errors on DNS or DHCP .. I'm at a loss what to look for next.. could this be a dodgy switch or piece of hardware?

 

Thanks in advance for any help...

[Jcx500]

Are they the same make/model, id check for windows updates or driver updates

[TechMonkey]

What IP address is it? Is it one you are expecting?

[bert113]

They are different makes and it random around the school, it could be one machine out of 30 it's bizarre..

[bert113]

They are getting the correct IP addresses, and I can release and renew perfectly fine they just can't browse anywhere but their own network

[TechMonkey]

Definitely sounds like a VLAN/DNS issue. Could it be you don't have listeners to both DCs so the few that have gone to the secondary are having issues?

 

EDIT: Have you looked at the Switch config to ensure the VLANS are setup the same? Could it be a certain switch? It may look random but all be going back to the same switch from different locations?

Edited November 23, 2020 by TechMonkey

[RobD]

Souns like a gateway issue to me. Check the subnet and Gateway are correct.

[Davit2005]

Ping the gateway on one of the PCs that is not working.

 

A bit more of a description of your network including running config of the core would be helpful, please take out any identifiable or private information.

 

Make sure vlans are tagged correctly and you have not got any network loops etc which are causing spanning tree issues.

Edited November 23, 2020 by Davit2005

[TechMonkey]

Gateway is a good call. Though would expect it to affect all or nothing.

[bald_pig]

Is there a pattern in the IP addresses of the machines that have the issue? I'm wondering if you aren't forwarding the whole ip range between VLANs?

[mavhc]

when you ping a new ip on a different vlan, what's the error? does the mac address for that ip appear in the arp cache?

[bert113]

Thank you all for your suggestions..

Bizarrely after a few hours some of the PC's start working again.. it's almost like something is being switched on that is causing the problems, I can go for a couple of days and the problem doesn't happen.

The default gateway for each machine is contactable and it's only a handful of PC's at a time on two vlans that have the problem, they are in different parts of the school and connect to different switches on the network, the only part that is the same is the vlan.

If it was effecting every machine on the two vlans I could understand but only a few are experiencing the problem at a time , it could be one out of an office of 4. It makes no sense...

[round2it]

static ip one thats not working see if it makes a difference

[mavhc]

one thing it might be is a limit on mac addresses due to port security

[kennysarmy]

DHCP?

 

You are n't running out of leases are you?