I'm not too conversant with switch vlan configurations, but here goes. A business has 3 switches in the only cab as follows:-
Procurve 2626 192.168.0.10 - Static IP
Procurve 2626 192.168.0.11 - Static IP
Procurve 2610-24/12PWR 192.168.0.47 (Yes that's correct .47) - Default VLAN DHCP/Bootp
Not sure who set this up but either way, the problematic switch seems to be the Procurve 2610-24/12PWR 192.168.0.47
The network was running slow several months ago and I noticed the Procurve 2610-24/12PWR had a conflicting ip address with a workstation. I rebooted the switches and the Procurve 2610-24/12PWR picked up an ip address of 192.168.0.30. For quickness I justed added this to the DHCP reservations to keep the business up and running at the time so that no other equipment picked up that address, as .30 is normally assigned to workstations ! It seemed to solve the issue for several months.
However, recently the network has been running slow again. Had to reboot and the switch is now on IP 192.168.0.47 which doesn't conflict. Someone set it up with an IP Configuration as "Default VLAN DHCP/Bootp". Even changing the setting to a "Manual" IP Address doesn't appear to rectify the issue. At the moment all is working, but it's sure to mess up again.
I'm assuming the issue is with the vlan configuration or DHCP issues. It's not essential that the business has a vlan now as apparently the domain has since been rebuilt since the switches were first installed. Looking at the DHCP on the server the 192.168.0.47 address is showing as inactive.