Overview
VTPv3 extends and enhances the functionality of VTP from previous versions. The operation of VTP is improved in three major areas:
- more secure administrative control: only a predefined device is allowed to update the VLAN topology
- extended functionality: VTPv3 supports the advertisement of extended range and private VLAN information
- support for MST
VTPv3 still retains the same core operation as previous versions. A VTP update message can be sent over a trunk but not over access ports or Layer 3 interfaces. Only devices in the same VTP domain are able to exchange and process VTP information.
In previous versions a new switch with the default domain name of NULL used the domain name of the first VTP message that it received. This behavior has changed with VTP version 3, which now requires manual configuration prior to enabling VTPv3.
Catalyst6500-1(config)# vtp version 3
Cannot set the version to 3 because domain name is not configured.
VTP messages that include a mismatching domain name are ignored and dropped.
Since the functional base in VTP version 3 is left unchanged from VTP version 2, so backward compatibility is built in. It is possible, on a per link basis, to automatically discover and support VTP version 2 devices
VTPv3 Enhancements
VTP version 3 added a number of enhancements to VTP version 1 and 2, including the following:
- support for extended range and private VLANs
- feature enhancement beyond support for a single database or VTP instance (MST support)
- protection from unintended database overrides
- option for clear-text or hidden password protection
- configuration option on a per-port basis instead of only on a global scheme
- optimized resource handling and more efficient transfer of information
While VTP version 1 and 2 interacted with the VLAN process directly, VTP version 3 introduces the concept of transferring opaque databases. This approach provides expanded usability, allowing independent databases (or tables) aka VTP instances that go beyond just serving the VLAN environment. VTP version 3 supports a VLAN instance and a separate MST instance.
In VTP version 3, the configuration revision number works the same as in previous versions, but only a specific devices in the domain, a primary server, is allowed to update other devices.
VTPv3 Operation
In addition to the three well-known roles (server, client, and transparent), a fourth role (off) is now available.
Transparent: Holds a locally created configuration on permanent storage (NVRAM). Does not
originate or evaluate received VTP advertisements. Relays received VTP messages on trunks if the STP state for VLAN 1 is forwarding. A domain check, as in VTP version 1, is not implemented.
Client: Holds received VTP information in temporary storage space. Local configuration is not
possible. The default MST configuration will be used at boot time until a VTP version 3
message arrives.
Off: Contrary to the transparent mode, the switch will not relay received VTP messages. Off
mode can be configured globally or on a per port basis. Formerly available only in CAT OS.
Server: VTPv3 expands and enhances the server role. By default, the secondary server subtype is applied. Only one server per domain can be prompted to be a primary server. Manual configuration on a secondary server locally is not possible. The role of a primary server for the VLAN database and MST database can be divided among two different physical devices if desired. When a device is designated as the primary server, a sanity check is performed in the domain. A warning message is generated if a conflicting device is discovered. The sanity check can be skipped be issuing the force keyword. If a secondary server is promoted to become a primary server without specifying VLAN or MST, the VLAN isntance is assumed.
No comments:
Post a Comment