What is the difference between vtp and 802.1q

ISL and The encapsulation and tagging methods identify a packet's source VLAN. This enables the switches to multiplex the traffic from multiple VLANs over a common trunk link. Chapter 8, "Trunking Technologies and Applications" describes these two methods and how they function. When Therefore, Cisco introduced the second generation trunk negotiation protocol, DTP. VTP provides a communication protocol between Catalysts over trunks. VTP does not work over non-trunk ports.

If you have a protocol analyzer capable of decoding these protocols and set it up to capture trunk traffic, it displays VTP as encapsulated within an ISL or Chapter 5 presented the three steps for creating a VLAN. Specifically, the steps include:.

Chapter 5 described the details of the last two steps, but deferred the discussion about VTP domains to this chapter. A VTP domain associates Catalysts with a common configuration interest. This helps to ensure administrative conformity between the Catalysts. The switch has received a VTP summary advertisement with a higher configuration revision than its own.

Upon receipt of an advertisement request, a VTP device sends a summary advertisement. One or more subset advertisements follow the summary advertisement. This is an example:. Start-Value —This is used in cases in which there are several subset advertisements. VTP server is the default mode. Off configurable only in CatOS switches —In the three described modes, VTP advertisements are received and transmitted as soon as the switch enters the management domain state.

Otherwise, there is no reason to use VTP V2. Changing the VTP version from 1 to 2 will not cause a switch to reload. The password must be the same password on all those switches.

However, there are occasions when VTP can create unnecessary traffic. All switches in the network receive all broadcasts, even in situations in which few users are connected in that VLAN. VTP pruning is a feature that you use in order to eliminate or prune this unnecessary traffic.

This figure shows a switched network without VTP pruning enabled. This figure shows the same switched network with VTP pruning enabled. VTP pruning takes effect several seconds after you enable it. By default, all switches are configured to be VTP servers.

This configuration is suitable for small-scale networks in which the size of the VLAN information is small and the information is easily stored in all switches in NVRAM.

In a large network, the network administrator must make a judgment call at some point, when the NVRAM storage that is necessary is wasteful because it is duplicated on every switch. At this point, the network administrator must choose a few well-equipped switches and keep them as VTP servers. Everything else that participates in VTP can be turned into a client.

The number of VTP servers should be chosen in order to provide the degree of redundancy that is desired in the network. Note: It is applicable only for CatOS. If a new Catalyst is attached in the border of two VTP domains, the new Catalyst keeps the domain name of the first switch that sends it a summary advertisement. Therefore, if you have two ends of a link that belong to different VTP domains, the trunk does not come up if you use DTP. In this special case, you must configure the trunk mode as on or nonegotiate , on both sides, in order to allow the trunk to come up without DTP negotiation agreement.

If the domain has a single VTP server and it crashes, the best and easiest way to restore the operation is to change any of the VTP clients in that domain to a VTP server. The configuration revision is still the same in the rest of the clients, even if the server crashes.

Therefore, VTP works properly in the domain.