Cisco Catalyst Switch Lab 2
Continuing from Lab 1 with a Catalyst 3550: factory reset, clean reconfiguration, VLANs, trunking, and STP root bridge priority.
This lab builds on Cisco Catalyst Switch Lab 1 (2950). Here, we add a Cisco Catalyst 3550 alongside the 2950 and configure a VLAN trunk and Spanning Tree Protocol (STP) root bridge priority.
Table of Contents
Initiating Factory Reset
1. Enter ROMMON mode
To start, on the Cisco Catalyst 3550 enter ROMMON mode:
- Unplug the power cable from the switch.
- Press and hold the MODE button on the front panel.
- While holding the MODE button, reconnect the power.
- Continue holding until you see the
switch:prompt in your console session (PuTTY).
This interrupts normal boot and forces the switch into the boot loader environment (ROMMON).
As in Lab 1, run the factory reset sequence on the 3550 (flash init, remove config, remove VLAN database).
Reconfigure Switch From Scratch
After the factory reset completes, proceed through the setup prompts in PuTTY (similar to the 2950 in Lab 1). When ready, Press RETURN to get started in the console.
Post Reconfigure from Scratch
1. Initial Configuration
Configure a management IP on VLAN 1 and set a default gateway for remote management.
2. Line Console Configuration
Enable logging synchronous on the console line so system messages don’t interrupt your typing.
3. VLAN Creation
Create VLAN 10 and VLAN 20 (Lab-1 and Lab-2), matching the 2950 configuration.
4. Show VLAN (Privileged EXEC)
Verify VLANs with show vlan from privileged EXEC mode.
5. Assign Switch Ports to VLANs
On the second switch, for example: place port 8 in VLAN 10 and port 16 in VLAN 20.
Trunk Port and Spanning Tree Protocol (STP)
Trunk Port: A trunk carries multiple VLANs over a single link using 802.1Q tags so the receiving switch knows each frame’s VLAN. Trunks commonly connect switches, or a switch to a router/firewall handling multiple VLANs. Here, VLAN 10 and VLAN 20 traffic must traverse between the 2950 and 3550 while remaining logically separated.
Spanning Tree Protocol (STP): STP prevents Layer 2 loops by placing redundant links in a blocking state, ensuring a single active path. If the active path fails, STP reconverges and activates an alternate path. In this lab, we set root bridge priority so the 3550 becomes the root for VLANs 10 and 20.
1. Set up the Trunk on Both Switches
Create a native VLAN (e.g., VLAN 99) on both switches and configure the trunk (e.g., on Fa0/24).
Catalyst 2950:
Catalyst 3550:
Display trunk info from privileged EXEC:
Catalyst 3550:
Catalyst 2950:
2. Configure STP Root Bridge Priority (VLAN 10 & VLAN 20)
Catalyst 2950:
Catalyst 3550:
Verify the STP state on both switches:
Catalyst 3550:
Catalyst 2950:
