Wireless vLAN implementations can allow broadcast and multicast traffic to "leak" across vLAN boundaries. Depending on the deployment, while running only IPv4, this might not cause any unusual observed behavior. Once some vLANs are enabled for IPv6, creating dual-stack or IPv6-only vLANs, IPv6 multicast traffic may leak onto IPv4-only subnets, resulting in connectivity problems. This issue was spotted (and solved) using the Cisco 1200AP. This brief describes the issue, and provides an explanation and solutions.