I have an office that has a layer 3 Dell switch in routing mode connected to both a Cisco router & a Dell Sonicwall.
The network has Vlan 1, 10, and 20.
The connection to the internet sits behind the Sonicwall.
The connection from the layer 3 switch to the Cisco router is in access mode for vlan 1.
The connection from the layer 3 switch to the Sonicwall is also in access mode vlan 1.
The default route on the layer 3 switch is to the Cisco router over Vlan 1.
The default route on the Cisco router is to the Sonicwall over Vlan 1.
My question is this, why does there need to be a route in the Sonicwall for the Vlans 10 & 20 to point back to the Layer 3 switch in order for network communication to work. Adding the routes at the Sonicwall allowed for inter vlan communication and outside internet access to work.
If I'm sitting on a computer that is connected to an access port 20 Vlan, how does my packet end up exiting the port connected to the Cisco router which is in access mode? Network diagram in simple design
Appreciate the assistance here everyone.