Switch Vlan Configuration

S#vlan database

S(vlan)#vlan <vlan number> name <vlan name> (vlan number range 1-1005)

S(config)#int VLAN 1 (allocate ip for management)

S(config-if)#ip address <ip addr> <subnet mask>

Allocates ports to vlans

S(config)#int f 0/1

S(config-if)#Switchport Mode Access

S(config-if)#Switchport Access vlan <vlan number>

Allocate port for a trunk

S(config)#int f0/4

S(config-if)#switchport mode trunk

S(config-if)#switchport trunk encapsulation [ isl | dot1q ] (don’t specify isl|dot1q on 2950’s)

Configure the VTP

S#vlan database

S(vlan)#vtp v2-mode

S(vlan)#vtp domain <name>

S(vlan)#vtp [ client | server | transparent ]

Configure the Switch for management access

S(config)#int VLAN 1

S(config-if)#ip address <ip addr> <subnet mask> (ip allocated to switch)

S(config)#ip default-gateway <ip addr> (ip of adjacent router subif)

Router show and debug commands

show vlan [brief]

show spanning-tree

debug sw-vlan packets

show vtp [ status | counters ]

Switching Types	Description	Benefit
Store and Forward	Complete Frame is received before forwarding	Most Latency, but best error checking
Cut Through (Also called fast forward	Only Destination Address read before forwarding	Least Latency, and no error checking
Fragment Free	Reads first 64bytes of data read before forwarding	Reasonable Latency and some error checking. Decides on error if < 64bytes.

Note: Bridges are Store and Forward by default. Switches are Fast Forward (cut through) by default.

Note: Adaptive Cut Through is Cut Through, but if errors detected, then it transitions to Store and Forward.