VTP vs. 802.1 q (and ISL)

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mohammedmahmoud Thu, 06/21/2007 - 05:45

Hi,

Trunking is a way to carry traffic from several VLANs over a point-to-point link between the two devices. Two ways that Ethernet trunking can be implemented are:

* Inter-Switch Link Protocol (ISL) (Cisco proprietary protocol)

* 802.1Q (IEEE standard)

In brief, VLAN Trunk Protocol (VTP) reduces administration in a switched network. When you configure a new VLAN on one VTP server, the VLAN is distributed through all switches in the domain. This reduces the need to configure the same VLAN everywhere. VTP is a Cisco-proprietary protocol that is available on most of the Cisco Catalyst series products.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

Edison Ortiz Thu, 06/21/2007 - 05:53

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12225see/scg/swvtp.htm

VTP

Understanding VTP

VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the addition, deletion, and renaming of VLANs on a network-wide basis. VTP minimizes misconfigurations and configuration inconsistencies that can cause several problems, such as duplicate VLAN names, incorrect VLAN-type specifications, and security violations.

Before you create VLANs, you must decide whether to use VTP in your network. Using VTP, you can make configuration changes centrally on one or more switches and have those changes automatically communicated to all the other switches in the network. Without VTP, you cannot send information about VLANs to other switches.

VTP is designed to work in an environment where updates are made on a single switch and are sent through VTP to other switches in the domain. It does not work well in a situation where multiple updates to the VLAN database occur simultaneously on switches in the same domain, which would result in an inconsistency in the VLAN database.

The switch supports 1005 VLANs, but the number of routed ports, SVIs, and other configured features affects the usage of the switch hardware. If the switch is notified by VTP of a new VLAN and the switch is already using the maximum available hardware resources, it sends a message that there are not enough hardware resources available and shuts down the VLAN. The output of the show vlan user EXEC command shows the VLAN in a suspended state.

VTP only learns about normal-range VLANs (VLAN IDs 1 to 1005). Extended-range VLANs (VLAN IDs greater than 1005) are not supported by VTP or stored in the VTP VLAN database.

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802.1q

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3560/12225see/scg/swvlan.htm

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