You want to split an Ethernet domain in two.

To split an Ethernet domain and ensure isolation of configuration and topology changes, the key mechanism is separating the VLAN management domains. This is achieved through:

VTP (VLAN Trunking Protocol) domain separation

Each VTP domain controls its own set of VLAN information and will not propagate VLAN changes across domain boundaries. By assigning unique VTP domain names to each half of the network, administrators prevent unintended synchronization of VLANs between switches.

Other options:

B. VTP password: Adds security but does not separate domains.

C. STP type: All switches in the domain can run the same or different STP versions and still be part of the same Ethernet domain.

D. VLAN ID: These can overlap across domains; uniqueness is not required to split domains.

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