# Managing Port Redundancy on Gigabit Ethernet I/O Modules

By default, the software manages port redundancy on Gigabit Ethernet I/O modules automatically.

If you manage port redundancy manually, the router retains the manual configuration after the module reboots.

You can monitor the port redundancy configuration with the show interfaces gigabitEthernet command and the show interfaces tenGigabitEthernet command.

| Note: The router manages failover in the same way for the Gigabit Ethernet I/O modules and the GE-2 SFP I/O module.

Managing port redundancy on GE I/O modules comprises the following set of tasks:

- Specifying the Timeout for Switchover to the Redundant Port
- Performing a Forced Switchover to the Redundant Port
- Specifying the Timeout for Switchover to the Redundant Port
- Disabling Port Redundancy

## Specifying the Timeout for Switchover to the Redundant Port

You can clear the ARP cache on an interface with redundant ports when the primary link fails by using the use the link failover arp-flush command.

To clear the ARP cache on an interface:

1. Specify the interface on which you want to clear the ARP cache.
   host1(config)#interface gigabitEthernet 1/0
2. Enable the ARP cache to be cleared when the primary link fails on the interface.
   host1(config-if)#link failover arp-flush

This feature enables the router to clear the ARP entries and obtain the media access control (MAC) address of the active link, thereby reducing the delay in learning new MAC addresses. Clearing the ARP cache after a link failover is supported on GE I/O modules with redundant ports.

Use the no version to maintain the ARP entries on the interface in the event of a failover.

## Performing a Forced Switchover to the Redundant Port

You can force a Gigabit Ethernet I/O module to switch operation from one port to the other by using the link failover force command.

To force the switchover from one port to another on a Gigabit Ethernet I/O module:

1. Select an interface on the Gigabit Ethernet I/O module on which you want to enable the failover from one port to the other.
   host1(config)#interface gigabitEthernet 5/0
2. Perform a forcible switchover from one port to another on the I/O module that contains redundant ports.
   host1(config-if)#link failover force

## Specifying the Timeout for Switchover to the Redundant Port

You can specify the time that the router waits for a port on a GE I/O module to become active before the router switches to the redundant port by using the link failover timeout command.

To specify a duration for which a router waits for a port to transition to the active state before the switchover to the redundant port occurs:

1. Select an interface on the GE I/O module for which you want to specify the timeout for switchover to the redundant port.
   host1(config)#interface gigabitEthernet 5/0
2. Specify a time in the range 100–10,000 milliseconds up to which the router waits for a port to become active before switching to the redundant port on the interface.
   host1(config-if)#link failover timeout 1000

   Use the no version to restore the default situation in which the router sets this time automatically.

## Disabling Port Redundancy

You can disable redundancy on a Gigabit Ehernet I/O module by allowing operation on the specified port only by using the link selection command.

To enable processing of traffic only on either the primary or secondary port in a redundant I/O module:

1. Select an interface on the Gigabit Ethernet I/O module on which you want to disable redundant port operations.
   host1(config)#interface gigabitEthernet 5/0
2. Enable the processing of traffic only on the secondary link of the interface.
   host1(config-if)#link selection secondary

   Use the no version to restore the default situation in which port redundancy is enabled.

#### Related Documentation

- Fast Ethernet I/O Modules Overview
- Gigabit Ethernet I/O Modules and IOAs Overview
- Configuring the Physical Interface
- link failover arp-flush
- link failover force
- link failover timeout
- link selection