Trunking
Trunk links are needed to pass VLAN info between switches. A port on a Cisco switch is either an access port or a
trunk port. Access ports belong to one VLAN and don’t offer any distinguishing marks on the frames that are passed
between switches. Access ports conjointly carry traffic that comes from solely the VLAN assigned to the port. A trunk
port is by default a member of all the VLANs that exist on the switch and carry traffic for all those VLANs between the
switches. to tell apart between the traffic flows, a trunk port should mark the frames with special tags as they pass
between the switches. Trunking may be a operate that has to be enabled on each side of a link. If 2 switches are
connected along, as an example, each switch ports should be configured for trunking, and that they should each be
organized with a similar tagging mechanism (ISL or 802.1Q).
S1
Switch>enable
Switch#configure terminal
Switch(config)#vlan 10
Switch(config-vlan)#name HR
Switch(config-vlan)#exit
Switch(config)#vlan 20
Switch(config-vlan)#name IT
Switch(config-vlan)#exit
Switch(config)#hostname S1
S1(config)#interface range fastEthernet 0/10 – 19
S1(config-if-range)#switchport mode access
S1(config-if-range)#switchport access vlan 10
S1(config-if-range)#exit
S1(config)#interface range fastEthernet 0/20 – 24
S1(config-if-range)#switchport mode access
S1(config-if-range)#switchport access vlan 20
S1(config-if-range)#exit
S1(config)#interface gigabitEthernet 0/1
S1(config-if)#switchport mode trunk
S1(config-if)#switchport trunk allowed vlan 10,20
S1(config-if)#switchport trunk native vlan 99
S2
Switch>enable
Switch#configure terminal
Switch(config)#vlan 10
Switch(config-vlan)#name HR
Switch(config-vlan)#exit
Switch(config)#vlan 20
Switch(config-vlan)#name IT
Switch(config-vlan)#exit
Switch(config)#hostname S2
S2(config)#interface range fastEthernet 0/10 – 19
S2(config-if-range)#switchport mode access
S2(config-if-range)#switchport access vlan 10
S2(config-if-range)#exit
S2(config)#interface range fastEthernet 0/20 – 24
S2(config-if-range)#switchport mode access
S2(config-if-range)#switchport access vlan 20
S2(config-if-range)#exit
S2(config)#interface gigabitEthernet 0/1
S2(config-if)#switchport mode trunk
S2(config-if)#switchport trunk allowed vlan 10,20
S2(config-if)#switchport trunk native vlan 99
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