New office, computers on network (wifi or ethernet) but no or limited internet connectivity

[jamietb]

I work in a small office and have just finished setting up a VLAN for VoIP phones and computers. 2 modem routers with 2 connections so the phones and computers and on different internet plans, but running through a smart switch. This is because our speeds are not great and we didn't want the phones to have low quality voice. We were on an office server in the old office but now with just have Synology NAS and just have local log ins for the computers.

All the computers seem to be running fine except 2 which sometimes will get an internet connection and sometimes they won't. You log in and sometimes you will connect straight away, sometimes wait 5 minutes and it will work and other times you still wait and never connect. WIthout the internet connection the can still access our NAS drive without any issues.

This happens on both WiFi and connected via ethernet.

I believe that it has something to do with trying to connect to the old server. I have tried reinstalling the network drivers
I have tried
Reset WINSOCK entries to installation defaults: netsh winsock reset catalog
Reset IPv4 TCP/IP stack to installation defaults. netsh int ipv4 reset c:\reset-4.log
Reset IPv6 TCP/IP stack to installation defaults. netsh int ipv6 reset c:\reset-6.log
http://embedonix.com/notes-blogs/how-to-fix-windows-10-no-internet-on-wifi-problem/

And
netsh int tcp set heuristics disabled

netsh int tcp set global autotuninglevel=disable

netsh int tcp set global rss=enabled

netsh int tcp show global
https://www.wiknix.com/how-to-fix-no-internet-access-in-windows-10/


When the computer loads up I can see for a brief microsecond that a cmd prompt pops up and I see the name of the old server pop up there. Does someone have any information on what I should do to fix this problem?

I try lots of things, restart the computer and everything is fine and I think that I have solved it. Then the next time I am in the office, the same problem happens again.

 

[jamietb]

OK, so I've done a bit more looking into it and I think it might be the way the switch was configured.
The IP address of the switch and the Netgear modem are both 192.168.0.1, so I was thinking of changing that to 192.168.0.2 (192.168.1.1 is the 2nd modem used for VoIP)
I also noticed that in the settings for the switch DHCP is disabled. Shouldn't this be enabled? When I do ipconfig /all is says DHCP Enabled: Yes

 

[boosted1g]

Modem and switch both having the same IP will cause some issues if PCs are going through that switch

Switch does not DHCP enabled if router is providing all DHCP.
Assuming this is a layer 3 switch then?