VLAN and Trunk
1. Broadcast
Broadcast domain: can listen to the same broadcast node combined to form a broadcast domain
The harm of broadcasting: When the broadcasting domain is getting bigger and bigger, the amount of broadcasting received per pc unit time is bigger! Will reduce the efficiency of communication!
How to reduce broadcast volume? Split broadcast domain/isolate broadcast domain! ! !
Routers can divide/isolate broadcast domains, and are natural devices that isolate broadcasts.
Disadvantages: high cost! not flexible! !
Two, VLAN
2.1 VLAN
Virtual Local Area Network
Virtual local area network
2.2 The role of VLAN
Logically split broadcast domain
Reduce broadcast volume
As shown:
2.3 How does VLAN control broadcast?
The switch does not allow people in different VLANs to communicate!
Only allow people in the same VLAN to communicate!
VLAN principle: on the same switch, the entrance and exit are not in the same VLAN, so they cannot pass through!
2.4 Configure static VLAN
1) Create VLAN
conf t
vlan ID
[name ceo]
exit
2) Add the port to the VLAN
int f0/1
switchport access vlan ID
sw ac vlan ID
exit
Enter multiple ports at once:
Switch(config)# int range f0/9 - 20
Switch(config-if-range)# sw ac vlan 30
3) View the VLAN table
show vlan b
2.5 VLAN-ID (just understand)
vlan-id：0 - 4095
0 can not be used, special purpose
4095 can not be used, special purpose
1-1001 I think it can be used
1006-2094
Three, TRUNK
3.1 Trunk overview
Trunk: is a public link between switches, which allows all VLANs to pass!
The data passing through the trunk link is added with a vlan label, and the label types of both parties must be agreed!
3.2 Label type
1) Cisco proprietary: ISL label
2) Internationally used: 802.1q
3.3 Trunk command
int f0/3
switchport mode trunk
sw m t
exit