Hello @TimMees60387,
your modem has no idea where to send the packets for your vlans. Your modem only knows the internal network 192.168.0.0/24 and has a default route to send anything else to the internet. So your internal vlans are unknown to your modem which means that it will never send traffic back to the switch for these vlans.
There are several possible solutions to this problem:
First, the best solution is to configure return routes for your internal vlans on your ISP modem/router if possible. So you need to check whether you can create such routes on your modem. Some modems offer this possibility, some don't. Check the documentation of your modem and see whether it supports adding routes for your internal vlans.
In case your modem does not support adding routes, then the next option is to configure NAT on your L3 switch if the switch supports it. You did not mention the exact model of your switch and what software you are running.
On a 3560CX with ipservice license running IOS version 15.2(7)E12, the necessary config looks like this:
interface GigabitEthernet0/1
ip nat outside
!
interface Vlan1
ip nat inside
!
interface Vlan2
ip nat inside
!
interface Vlan6
ip nat inside
!
access-list 10 permit 192.168.10.0 0.0.0.255
access-list 10 permit 192.168.20.0 0.0.0.255
access-list 10 permit 192.168.60.0 0.0.0.255
!
ip nat inside source list 10 interface gi0/1 overload
The disadvantage of this solution is the fact that you use NAT two times, i.e. on your switch and on your modem, which can affect the performance and might cause problems e.g. with VPN protocols.
If your switch does not support NAT or you want to avoid double-natting, then you need to place a router between your switch and ISP modem. In that case the configuration of your modem should be changed to pass-through to avoid double-natting.
In case of a cisco router the config would look very similar to the one for the switch.
Hence you need to check your options and then decide the best way to go. Let us know if you need further help.
HTH!
