Ethernet loopback configuration considerations

The configuration considerations for Ethernet loopback are as follows:

  • An interface port cannot be configured in both flow-aware and flow-unaware modes simultaneously.
  • An interface port cannot be configured in both VLAN-aware and VLAN-unaware modes simultaneously.
  • The source MAC address and destination MAC address which define the flow-aware configuration must be unicast MAC addresses.
  • The source MAC address configured in the flow-aware configuration must be unique across the network.
  • Ports can be added or removed in different Ethernet loopback modes.
  • A flow-aware configuration can be added on an in-service Ethernet loopback port.
  • A flow-aware configuration on a port cannot be removed from an in-service Ethernet loopback port.
  • The Ethernet loopback configuration is persistent across reboots if the configuration is saved. This will help to measure switching time at reload time from a remote device.
  • Ethernet loopback cannot be enabled when one or more of the following features are configured:
    • ACL
    • 802.1X port security
    • Traffic shaping
    • Dual mode
    • Rate limiting
  • Ethernet loopback depends on ACL entry availability because it uses ACL resources.
  • MAC learning is supported for a packet that is looped back in devices.
  • Static MAC configuration is not allowed globally when Ethernet loopback is configured in the system.
  • When Ethernet loopback is enabled, the packets are looped back at the rate received. However, the packets can be dropped potentially when the device is oversubscribed.
  • Ethernet loopback is supported on the physical interface and LAG interface.
  • Ethernet loopback can be enabled only on an existing LAG.
  • An Ethernet loopback-enabled LAG cannot be undeployed.
  • An Ethernet loopback-enabled port cannot be added to an existing LAG.
  • VLAN priority remarking is not allowed on an Ethernet loopback-enabled port.
  • The state of the port (up or down) does not affect the Ethernet loopback functionality.
  • Ethernet loopback configuration is not allowed on multi-range VLAN (MVLAN), VLAN Group, or VLAN Range.
  • Ethernet loopback cannot be configured on a set of VLANs that share a Layer 2 topology (Topology Group).
  • Ethernet loopback must be configured in a loop-free network for better results.
  • Configuring Ethernet loopback on an MCT ICL port is not recommended as it may impact MCT operations.

Parent topic: Ethernet loopback