Understanding Cisco VTP
The preceding section briefly alluded to another LAN protocol called VTP. VTP reduces administration overhead in a switched network. With VTP, when you configure a new VLAN on a switch designated as a VTP server, information regarding that VLAN is distributed to all switches in the VTP domain, thereby removing the need to manually configure each switch one by one. You can configure a switch to operate in one of four different VTP modes:
• Server. Here, you can create, modify, and delete VLANs and specify other configuration parameters, such as VTP version and VTP pruning, for the entire VTP domain. VTP servers advertise their VLAN configuration to other switches in the same VTP domain and synchronize their VLAN configuration with other switches based on advertisements received over trunk links. VTP server is the default mode.
• Client. VTP clients behave the same way as VTP servers, but you cannot create, change, or delete VLANs on a VTP client.
• Transparent. VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN configuration, and it does not synchronize its VLAN configuration based on received advertisements; however, in VTP version 2, transparent switches forward VTP advertisements that they receive out of their trunk ports. They act like a transparent wire with regards to VTP messages: They forward them without processing them.
• Off. In the three previous modes, VTP advertisements are received and sent as soon as the switch enters the management domain state. In VTP Off mode, switches behave the same as in VTP Transparent mode, except that VTP advertisements are not forwarded, but dropped.
A VTP domain comprises switches that share a common VTP domain name. VTP reduces the need to manually configure the same VLAN everywhere. VTP is a Cisco-proprietary protocol that is available on most Cisco Catalyst series products. Three versions of the protocol exist: VTP v1, v2, and v3. Versions 1 and 2 are almost identical. (Version 2 simply introduced support for Token Ring VLANs.) Version 3 represents a major overhaul of the protocol that was motivated in part by certain security considerations.
Continue reading here: DHCP Overview
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