The scenario describes two separate VSX clusters interconnected via MC-LAG, where both clusters are configured to use theexact samevirtual IP address and virtual MAC address for their respective Active Gateway SVIs.

Active Gateway Scope & Conflict:Active Gateway provides a highly available default gatewaywithina single VSX cluster (L2 domain). The vIP/vMAC combination should be unique within its L2 broadcast domain.

Interconnecting Clusters with Same vIP/vMAC:When two VSX clusters using the identical Active Gateway vIP/vMAC are interconnected at Layer 2 (even via MC-LAG), this creates a situation where the same active L2 (vMAC) and L3 (vIP) address exists in multiple places within the extended broadcast domain.

Consequences:This leads to MAC address conflicts and L3 ambiguity. ARP resolution becomes unreliable, potentially causing ARP tables to flap on connected devices. Traffic forwarding becomes unpredictable, as packets destined for the vIP/vMAC might be delivered to the "wrong" cluster. This unstable and unpredictable state is sometimes referred to as an asymmetric or "async" setup.

Analysis of Options:

A: ISL traffic might change, but it's a symptom, not the root problem.

B: Multiple ARP replies would occur, contributing to the confusion.

C: The configuration results in an "async setup," accurately describing the unstable state caused by duplicate active L2/L3 addresses across the interconnected L2 domain.

D: Load-balancing happens within a cluster; this setup causes conflict, not predictable load balancing across clusters.

Conclusion:Reusing the same Active Gateway vIP and vMAC across interconnected VSX clusters is not a valid design and leads to an unstable, asymmetric ("async") environment due to address duplication within the extended L2 domain. Option C best describes this problematic outcome.