Distribution Layer Switch Configuration

The Distribution Layer (Layer 3 Switch) acts as the bridge between your Access Layer switches and your Core Routers. In the Smart Campus topology, this switch handles both single-VLAN traffic coming from specific departments and multi-VLAN traffic going to the router.

1. Configuring Downlinks (Connecting to Access Switches)

In our specific campus design, each Access switch is dedicated to a single department (e.g., the Admin switch is entirely VLAN 10). Therefore, the port on the Distribution switch connecting to the Admin switch only needs to carry VLAN 10 traffic, making it an Access Port.

enable

configure terminal

interface gig1/0/2

switchport mode access

switchport access vlan 10

exit

do wr

• switchport mode access: Forces the interface to only accept traffic for a single assigned VLAN.

• switchport access vlan 10: Assigns this specific link to the Admin network. (Note: This is repeated for gig1/0/3 for VLAN 20, etc.)

2. Configuring Uplinks (Connecting to Core Routers)

The cable connecting the Layer 3 switch up to the Core Router must carry traffic from all departments so the router can perform Inter-VLAN routing. Therefore, this port must be configured as a Trunk Port.

interface gig1/0/1

switchport trunk encapsulation dot1q

switchport mode trunk

exit

do wr

• switchport trunk encapsulation dot1q: Tells the Layer 3 switch to use the IEEE 802.1Q standard to tag VLAN frames. (Note: Layer 2 switches do this automatically, but Cisco Layer 3 switches require you to specify the encapsulation protocol first).

• switchport mode trunk: Forces the interface to operate as a trunk link, allowing traffic from Admin, IoT, Students, and all other VLANs to pass through to the core router.

3. Powering on Layer 3 Switches (Packet Tracer Tip)

By default in Cisco Packet Tracer, Layer 3 switches (like the 3650 model) are powered off.

• You must physically drag the AC Power Supply into the empty slot on the device's back panel before the CLI will become active.

4. Saving the Configuration

Always save your configuration so the routing and VLAN database are not lost during a reboot.

copy running-config startup-config