Asr 5000 System Administration Guide, Staros Release 21.1 - Cisco ASR 5000 Administration Manual

Configuring Line Card and SPIO Port Redundancy
To ensure that system line card and port-level redundancy mechanisms function properly, disable the
Caution
Spanning Tree protocol on devices connected directly to any system port. Failure to turn off the Spanning
Tree protocol may result in failures in the redundancy mechanisms or service outage.
By default, the system provides port-level redundancy when a failure occurs, or you issue the port switch to
command. In this mode, the ports on active and standby line cards (for example, 17/1 and 33/1) have the same
MAC address, but since only one of these ports may be active at any one time there are no conflicts. This
eliminates the need to transfer MAC addresses and send gratuitous ARPs in port failover situations. Instead,
for Ethernet ports, three Ethernet broadcast packets containing the source MAC address are sent so that the
external network equipment (switch, bridge, or other device) can re-learn the information after the topology
change. However, if an line card removal is detected, the system sends out gratuitous ARPs to the network
because of the MAC address change that occurred on the specific port.
With port redundancy, if a failover occurs, only the specific port(s) become active. For example; if port 17/1
fails, then port 33/1 becomes active, while all other active ports on the line card in slot 17 remain in the same
active state. In port failover situations, use the show port table or show linecard table commands to check
that ports are active on both cards and that both cards are active.
Take care when administratively disabling a port that is one of a redundant pair. A redundant pair comprises
both the active and standby ports—for example 17/1 and 33/1. If 17/1 is active, administratively disabling
17/1 through the CLI does not make 33/1 active. It disables both 17/1 and 33/1 because an action on one port
has the same effect on both. Refer to Enabling Line Card and SPIO Redundancy below, and Creating and
Configuring Ethernet Interfaces and Ports in System Interface and Port Configuration Procedures.
If card-level redundancy is initiated, there is no port-level redundancy in a line card or SPIO failover. The
standby line card or SPIO becomes active and all ports on that card become active. With line cards, the system
automatically copies all the MAC addresses and configuration parameters used by the failed line card to its
redundant counterpart. The ports on SPIOs keep their original MAC addresses, and the system automatically
copies the failed SPIO's configuration parameters to its redundant counterpart. The packet processing card
automatically re-routes to its redundant line card.
With the SPIO cards, any time there is a port or card switch gratuitous ARPs are sent.
Be aware that in the case of a system with only one SMC and two SPIO cards, both SPIOs come up online.
Important
Automatic switching of Ethernet ports does not occur in this scenario, but you can initiate card and port
switching by using the card spio switch to and port switch to commands.
Port redundancy can be configured to be revertive or non-revertive. With revertive redundancy service is
returned to the original port when service is restored.

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System Settings