The Inter-Switch Link (ISL) is a fundamental component of an AOS-CX Virtual Switching Extension (VSX) pair. It serves both as a Layer 2 forwarding path between the VSX peers and as the principal control-path channel used to synchronize operational state between the two switches.
HPE Aruba Networking explicitly identifies the MAC table as one of the data structures synchronized across the VSX ISL. Other synchronized information includes the ARP table, LACP state for VSX LAGs, and MSTP state. This synchronization enables both independent VSX switches to maintain consistent forwarding information and support resilient multi-chassis LAG operation. Aruba Networking
The architecture is important because VSX does not merge both switches into a single control plane. Each peer retains its own control plane, while selected operational databases and protocol states are synchronized through the ISL. HPE ' s Campus Design guidance similarly states that VSX peers synchronize MAC, ARP, STP, and other state tables across the ISL. Aruba Networking
An SVI is configuration rather than the requested synchronized forwarding-table information. UDLD is a link-detection protocol, and RPVST+ is not the answer identified in Aruba ' s ISL synchronization list.
Study Guide Topics: AOS-CX VSX, Inter-Switch Link, VSX Synchronization, MAC Address Tables, ARP Synchronization, LACP State, MSTP State.
