Switches use network bridging to facilitate the interconnection of local area networks (LANs) so that traffic can be exchanged between devices. Bridging occurs at layer 2 of the OSI model.

When creating network bridges on HPE switches, network administrators can configure MAC addressing, VLANs, and various loop prevention protocols.

Devices on a network are identified by their MAC address. The switch maintains a MAC address table where it stores information about the other Ethernet interfaces to which a switch is connected. The table enables the switch to send outgoing data (Ethernet frames) on the specific port required to reach its destination, instead of broadcasting the data on all ports (flooding).

VLANs are primarily used to provide network segmentation at layer 2. VLANs enable the grouping of users by logical function instead of physical location. Layer 2 VLANs can be associated with a single physical port, or multiple aggregated ports (referred to as LAG, short form for Link Aggregation). Link Aggregation enables a logical grouping of individual interfaces to function as a single, higher-speed link, providing dramatically increased bandwidth. This mechanism provides network resiliency when individual link failures occur. Aruba switches include advanced network resiliency through MCLAG (Multi Chassis Link Aggregation) which offers network resiliency on individual device failure as well.

When multiple individual links are connected to one another, there is a possibility that multiple paths (loops) will exist between devices. Loops reduce network operational efficiency. ArubaOS-CX provides several features to detect and avoid loops, including:

  • MSTP: Multiple-Instance spanning tree protocol (MSTP) ensures that only one active path exists between any two nodes in a spanning tree instance. A spanning tree instance comprises a unique set of VLANs, and belongs to a specific spanning tree region. A region can comprise multiple spanning tree instances (each with a different set of VLANs), and allows one active path among regions in a network.
  • RPVST+: Rapid Per VLAN Spanning Tree+ (RPVST+) is an updated implementation of STP (Spanning Tree Protocol). It enables the creation of a separate spanning tree for each VLAN on a switch, and ensures that only one active, loop-free path exists between any two nodes on a given VLAN.
  • Loop Protection: In cases where spanning tree protocols cannot be used to prevent loops at the edge of the network, loop protection may provide a suitable alternative. Loop protection can find loops in untagged layer 2 links, as well as on tagged VLANs.

ArubaOS-CX also supports the MVRP (Multiple VLAN Registration Protocol), a registration protocol defined by IEEE, which propagates VLAN information dynamically across devices. It also enables devices to learn and automatically synchronize VLAN configuration information, reducing the configuration workload.

Additionally, ArubaOS-CX supports the Unidirectional Link Detection (UDLD) protocol. UDLD monitors the link between two network devices, and if the link fails, blocks the ports on both ends of the link. UDLD is useful for detecting failures in fiber links and trunks.