Thursday, September 24, 2009

VTP

What is VTP?

VTP allows a network manager to configure a switch so that it will propagate VLAN configurations to other switches in the network. The switch can be configured in the role of a VTP server or a VTP client. VTP only learns about normal-range VLANs (VLAN IDs 1 to 1005). Extended-range VLANs (IDs greater than 1005) are not supported by VTP.


Benefits of VTP
-VLAN configuration consistency across the network
-Accurate tracking and monitoring of VLANs
-Dynamic reporting of added VLANs across a network
-Dynamic trunk configuration when VLANs are added to the network


VTP Components

VTP Domain-Consists of one or more interconnected switches. All switches in a domain share VLAN configuration details using VTP advertisements. A router or Layer 3 switch defines the boundary of each domain.

VTP Advertisements-VTP uses a hierarchy of advertisements to distribute and synchronize VLAN configurations across the network.

VTP Modes- A switch can be configured in one of three modes: server, client, or transparent.

VTP Server-VTP servers advertise the VTP domain VLAN information to other VTP-enabled switches in the same VTP domain. VTP servers store the VLAN information for the entire domain in NVRAM. The server is where VLANs can be created, deleted, or renamed for the domain.

VTP Client-VTP clients function the same way as VTP servers, but you cannot create, change, or delete VLANs on a VTP client. A VTP client only stores the VLAN information for the entire domain while the switch is on. A switch reset deletes the VLAN information. You must configure VTP client mode on a switch.

VTP Transparent-Transparent switches forward VTP advertisements to VTP clients and VTP servers. Transparent switches do not participate in VTP. VLANs that are created, renamed, or deleted on transparent switches are local to that switch only.

VTP Pruning-VTP pruning increases network available bandwidth by restricting flooded traffic to those trunk links that the traffic must use to reach the destination devices. Without VTP pruning, a switch floods broadcast, multicast, and unknown unicast traffic across all trunk links within a VTP domain even though receiving switches might discard them.


Summary Advertisements contain the VTP domain name, the current revision number, and other VTP configuration details.

Summary advertisements are sent:
-Every 5 minutes by a VTP server or client to inform neighboring VTP-enabled switches of the current VTP configuration revision number for its VTP domain
-Immediately after a configuration has been made


It may take multiple subset advertisements to fully update the VLAN information.
Changes that trigger the subset advertisement include:
-Creating or deleting a VLAN
-Suspending or activating a VLAN
-Changing the name of a VLAN
-Changing the MTU of a VLAN

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