98 Cisco LAN Switching Configuration Handbook
Core_1(config-if)# switchport encapsulation negotiate
Core_1(config-if)# switchport mode dynamic auto
Core_1(config-if)# switchport trunk allowed vlan allowed 1,10
Core_1 (config-if)# end
Core_1# copy running-config startup-config
An example of the Layer 2 IOS configuration for Access_1 follows:
Access_1 (config)# interface gigabitethernet 0/1
Access_1 (config-if)# switchport mode trunk
Access_1 (config-if)# switchport trunk encapsulation dot1q
Access_1 (config-if)# switchport trunk allowed vlan allowed 5,8,10
Access_1 (config-if)# end
Access_1# copy running-config startup-config
6-4: VLAN Trunking Protocol
■ VTP sends messages between trunked switches to maintain VLANs on these switches
to properly trunk.
■ VTP is a Cisco proprietary method of managing VLANs between switches and runs
across any type of trunking mechanism.
■ VTP messages are exchanged between switches within a common VTP domain.
■ VTP domains must be defined or VTP disabled before a VLAN can be created.
■ Exchanges of VTP information can be controlled by passwords.
■ VTP manages only VLANs 2 through 1002.
■ VTP allows switches to synchronize their VLANs based on a configuration revision
number.
■ Switches can operate in one of three VTP modes: server, transparent, or client.
■ VTP can prune unneeded VLANs from trunk links.
Enabling VTP for Operation
VTP exists to ensure that VLANs exist on the local VLAN database of switches in a
trunked path. In addition to making sure the VLANs exist, VTP can further synchronize
name settings and can be used to prune VLANs from trunk links that are destined for
switches that do not have any ports active in that particular VLAN.
To manage and configure VTP, use the following steps.
1. Activate VTP on a switch.
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