Network Port not serving DHCP to PCs

[mdrabble]

Got a very weird issue..... I have switch which is refusing to handout IP addresses to computers but will happily give out IP addresses to my network tester.

 

All switches are Unifi EdgeMax Lites (Black ones) running the latest firmware 1.9.3

 

I have VLANs in place, but not a VLAN issue as the network tester gets the correct VLAN IP

 

I have tried rebooting the switch but problem still exists

 

If I move the PCs to a different switch, they happily get an IP address.

 

If I move a known working PC to this switch, it fails to get an IP address.

 

So I am left scratching my head - why is the tester getting IP address but nothing else?

 

Anyone got any other ideas i can try?

 

Edit: Going to try resetting the the switch and reapplying the config tomorrow.

 

Cheers

Edited April 21, 2022 by mdrabble

[mdrabble]

Well decided to stay late and try resetting the switch and it has confirmed that it is some kind of VLAN issue

 

If I put the ports affected onto a different VLAN, the PCs pick up a valid IP address. Soon as I put them back on the correct VLAN, they fail to pick up a valid IP address.

 

Which leaves me even more confused!!

 

Nothing has changed on the config for the Core Switch or Edge Switch, so not sure what else to look at.

 

I've clear the ARP cache of the core switch and that still did nothing - so as a last resort, I could try rebooting the core switch.

 

But if anyone else has any ideas please give me a shout.

 

Cheers

[eddyc]

Probably a silly suggestion, but are there enough free IP addresses in that DHCP pool for the number of devices in the VLAN?

 

eddyc

[mdrabble]

Probably a silly suggestion, but are there enough free IP addresses in that DHCP pool for the number of devices in the VLAN?

 

eddyc

 

Must admit not checked that but there should enough as lease times are approx 7 days and half the network been off due to half term - but that said, I’ll check that in the morning when I’m back in school.

[mdrabble]

DHCP has plenty of addresses available, so that rules that option out - but good idea to check.

 

So.... my brain is turning to mush......

 

put PC on different VLAN, PC works fine and gets a valid IP address

put PC back on on desktop VLAN and it fails to get an IP addresses

move PC to another part of network and works fine.

 

Here is the weird part...... other side of the room is on the same switch and works fine, but even if I move the PC over to the working side, it still doesnt work........

 

:confused::confused:

 

Anyone any ideas?

 

Cheers

[steveg]

There isn't a mac address filter on the dhcp server for that vlan is there?

[mdrabble]

There isn't a mac address filter on the dhcp server for that vlan is there?

 

Nope, Haven’t set up any filters etc.

 

I’m taking the drastic measure of rebooting the core switch to see if anything was stuck in the arp cache as it should just work.

[mdrabble]

Looks like rebooting the core switch has cured the issue!

 

No idea what, why or how it got confused but at least it now working.

 

Cheers