Day 4

1. Vlan
2. Spanning Tree

1. Vlan
Vlans let network administrator create multiple virtual broadcast domains in a single switch.
Hosts between differnent Vlans cannot communicate without a router or a layer 3 device.

By default, Cisco switches has one Vlan, which is Vlan1 and all the switch ports are in Vlan1.

Following config depicts how to create a new Vlan (vlan 2) and move port 1 to newly created vlan. Configuration is for Cisco 2900 XL series switch.



2. Spanning Tree
Multiple connections between switches cause traffic loop which in turn leads to traffic/broadcast storms.
Multiple connections between switches are desirable for redundancy.

Spanning tree allows multiple inter-switch connections by automatically blocking one of the connections leaving only one active connection. In case of active connection failure, blocking port will become the active one.