You have peered two virtual networks. However, traffic is not flowing between them. What is the most likely cause?

Correct answer: Peering state is not 'Connected'

Option C is correct because VNet peering requires both sides to show a 'Connected' state before traffic can flow; if either side is in 'Initiated', 'Disconnected', or any other non-Connected state, packets are dropped. Option A is incorrect because NSG rules can certainly block traffic, but this is not the most likely cause when peering was just established and no traffic flows at all; a disconnected peering state is the first thing to check. Option B is incorrect because virtual machines residing in different resource groups has no effect on VNet peering or traffic routing between peered networks. Option D is incorrect because VNet peering automatically injects system routes for the peered address space, so a missing user-defined route table is not the primary cause of a complete traffic failure.