Configuring Mio/Umio Port Redundancy - Cisco ASR 5500 Administration Manual

Configuring MIO/UMIO Port Redundancy

Configuring MIO/UMIO Port Redundancy
Port redundancy for MIO cards provides an added level of redundancy that minimizes the impact of network
failures that occur external to the system. Examples include switch or router port failures, disconnected or cut
cables, or other external faults that cause a link down error.
Caution To ensure that system card and port-level redundancy mechanisms function properly, disable the 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 MIO/UMIO cards 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 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 5/1
fails, then port 6/1 becomes active, while all other active ports on the line card in slot 5 remain in the same
active state. In port failover situations, use the show port table command 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 5/1 and 6/1. If 5/1 is active, administratively disabling 5/1
through the CLI does not make 6/1 active. It disables both 5/1 and 6/1 because an action on one port has the
same effect on both. Refer to Creating and Configuring Ethernet Interfaces and Ports in System Interface
and Port Configuration Procedures.
With automatic card-level redundancy, there is no port-level redundancy in an MIO/UMIO failover. The
standby MIO/UMIO becomes active and all ports on that card become active. The system automatically copies
all the MAC addresses and configuration parameters used by the failed MIO/UMIO to its redundant counterpart.
The ports on MIOs keep their original MAC addresses, and the system automatically copies the failed
MIO/UMIO's configuration parameters to its redundant counterpart.
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.
ASR 5500 System Administration Guide, StarOS Release 19
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System Settings