Preventing VLAN Database Corruption

A

When adding an old switch back into a network, it is important to ensure that it does not corrupt the VLAN database. This can be done by taking certain precautions during the re-introduction of the switch.

Firstly, it is important to understand the role of VTP (VLAN Trunking Protocol) in managing VLANs in a network. VTP allows VLAN configuration information to be propagated to other switches in the same VTP domain. When a switch is added to a VTP domain, it will receive the VLAN configuration information from the other switches in the domain.

Now, coming to the answers provided:

A. Add the switch in the VTP domain with a lower revision number.

This is a correct option. VTP uses revision numbers to determine which VLAN configuration is more recent. When a switch with a higher revision number is introduced into the network, it will overwrite the VLAN configuration of the other switches in the same VTP domain. However, when a switch with a lower revision number is introduced, it will not overwrite the VLAN configuration of the other switches. Therefore, adding the switch with a lower revision number will prevent it from corrupting the VLAN database.

B. Add the switch in the VTP domain with a higher revision number.

This option is not recommended as it can cause the VLAN configuration of other switches to be overwritten by the new switch.

C. Add the switch with DTP set to dynamic desirable.

DTP (Dynamic Trunking Protocol) is used to negotiate trunking between two switches. Setting DTP to dynamic desirable means that the switch will actively try to form a trunk with the neighboring switch if it supports DTP. However, this does not directly prevent the switch from corrupting the VLAN database.

D. Add the switch with DTP set to desirable.

This option is similar to option C, and does not directly prevent the switch from corrupting the VLAN database.

Therefore, the correct answer is A - Add the switch in the VTP domain with a lower revision number.