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.

You can perform auto link selection by removing the cables from either the primary or the secondary link. It automatically switches over to its redundant link. By default, the Duplex mode is set to Auto negotiate for Gigabit Ethernet. If the link is set to auto failover to the redundant link, then the Mac layer delays the link status notification to the upper layer during the Auto link selection.

Note: By manually setting the Admin duplex mode to Full, Mac updates the link status to the upper layer immediately. When the router is connected to a switch, Failover time depends on the router port and switch port settings. In such cases, the link failover timeout is not sufficient to handle link failover mechanism. If link failover takes more time, the link may fail to switchover within the failover time, and the link failure status is sent to upper layer.

Performing link selection manually from the command line interface disables the Port link redundancy feature. If you use the link selection primary | secondary command, the link selection is performed without using redundancy feature. This results in link Up and Down events.

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

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 Ethernet 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.