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Configuring Routing Engine Redundancy

The following sections describe how to configure Routing Engine redundancy:

Note: To complete the tasks in the following sections, re0 and re1 configuration groups must be defined. For more information about configuration groups, see the JUNOS CLI User Guide.

Modifying the Default Routing Engine Mastership

For routers with two Routing Engines, you can configure which Routing Engine is the master and which is the backup. By default, the Routing Engine in slot 0 is the master (re0) and the one in slot 1 is the backup (re1).

Note: In systems with two Routing Engines, both Routing Engines cannot be configured to be master at the same time. This configuration causes the commit check to fail.

To modify the default configuration, include the routing-engine statement at the [edit chassis redundancy] hierarchy level:


            
               [edit chassis redundancy]
               routing-engine slot-number (master | backup | disabled);

slot-number can be 0 or 1. To configure the Routing Engine to be the master, specify the master option. To configure it to be the backup, specify the backup option. To disable a Routing Engine, specify the disabled option.

Note: To switch between the master and the backup Routing Engines, you must modify the configuration and then activate it by issuing the commit synchronize command.

Configuring Automatic Failover to the Backup Routing Engine

The following sections describe how to configure automatic failover to the backup Routing Engine when certain failures occur on the master Routing Engine.

Without Interruption to Packet Forwarding

For routers with two Routing Engines, you can configure graceful Routing Engine switchover (GRES). When graceful switchover is configured, socket reconnection occurs seamlessly without interruption to packet forwarding. For information about how to configure graceful Routing Engine switchover, see Graceful Routing Engine Switchover Configuration Guidelines.

On Detection of a Hard Disk Error on the Master Routing Engine

After you configure a backup Routing Engine, you can direct it to take mastership automatically if it detects a hard disk error from the master Routing Engine. To enable this feature, include the failover on-disk-failure statement at the [edit chassis redundancy] hierarchy level.


            
               [edit chassis redundancy]
               failover on-disk-failure;

On Detection of a Loss of Keepalive Signal from the Master Routing Engine

After you configure a backup Routing Engine, you can direct it to take mastership automatically if it detects a loss of keepalive signal from the master Routing Engine.

To enable failover on receiving a loss of keepalive signal, include the failover on-loss-of-keepalives statement at the [edit chassis redundancy] hierarchy level:


            
               [edit chassis redundancy]
               failover on-loss-of-keepalives;

When graceful Routing Engine switchover is not configured, by default, failover occurs after 300 seconds (5 minutes). You can configure a shorter or longer time interval. To change the keepalive time period, include the keepalive-time statement at the [edit chassis redundancy] hierarchy level:


            
               [edit chassis redundancy]
               keepalive-time seconds;

The range for keepalive-time is 2 through 10,000 seconds.

The following example describes the sequence of events if you configure the backup Routing Engine to detect a loss of keepalive signal in the master Routing Engine:

Manually configure a keepalive-time of 25 seconds.
After the Packet Forwarding Engine connection to the primary Routing Engine is lost and the keepalive timer expires, packet forwarding is interrupted.
After 25 seconds of keepalive loss, a message is logged, and the backup Routing Engine attempts to take mastership. An alarm is generated when the backup Routing Engine becomes active, and the display is updated with the current status of the Routing Engine.
After the backup Routing Engine takes mastership, it continues to function as master.

Note: When graceful Routing Engine switchover is configured, the keepalive signal is automatically enabled and the failover time is set to 2 seconds. You cannot manually reset the keepalive time.

A former master Routing Engine becomes a backup Routing Engine if it returns to service after a failover to the backup Routing Engine. To restore master status to the former master Routing Engine, you can use the request chassis routing-engine master switch operational mode command.

If at any time one of the Routing Engines is not present, the remaining Routing Engine becomes master automatically, regardless of how redundancy is configured.

When a Software Process Fails

To configure automatic switchover to the backup Routing Engine if a software process fails, include the failover other-routing-engine statement at the [edit system processes process-name] hierarchy level:


            
               [edit system processes] process-name
               failover other-routing-engine;

process-name is one of the valid process names. If this statement is configured for a process, and that process fails four times within 30 seconds, the router reboots from the other Routing Engine. Another statement available at the [edit system processes] hierarchy level is failover alternate-media. For information about the alternate media option, see the JUNOS System Basics Configuration Guide.

Manually Switching Routing Engine Mastership

To manually switch the Routing Engine mastership, use one of the following commands:

On the backup Routing Engine, request that the backup Routing Engine take mastership by issuing the request chassis routing-engine master acquire command.
On the master Routing Engine, request that the backup Routing Engine take mastership by using the request chassis routing-engine master release command.
On either Routing Engine, switch mastership by issuing the request chassis routing-engine master switch command.

Verifying Routing Engine Redundancy Status

A separate log file is provided for redundancy logging at /var/log/mastership. To view the log, use the file show /var/log/mastership command. Table 5 lists the mastership log event codes and descriptions.

Table 5: Routing Engine Mastership Log

Event Code	Description
E_NULL = 0	The event is a null event.
E_CFG_M	The Routing Engine is configured as master.
E_CFG_B	The Routing Engine is configured as backup.
E_CFG_D	The Routing Engine is configured as disabled.
E_MAXTRY	The maximum number of tries to acquire or release mastership was exceeded.
E_REQ_C	A claim mastership request was sent.
E_ACK_C	A claim mastership acknowledgement was received.
E_NAK_C	A claim mastership request was not acknowledged.
E_REQ_Y	Confirmation of mastership is requested.
E_ACK_Y	Mastership is acknowledged.
E_NAK_Y	Mastership is not acknowledged.
E_REQ_G	A release mastership request was sent by a Routing Engine.
E_ACK_G	The Routing Engine acknowledged release of mastership.
E_CMD_A	The command request chassis routing-engine master acquire was issued from the backup Routing Engine.
E_CMD_F	The command request chassis routing-engine master acquire force was issued from the backup Routing Engine.
E_CMD_R	The command request chassis routing-engine master release was issued from the master Routing Engine.
E_CMD_S	The command request chassis routing-engine master switch was issued from a Routing Engine.
E_NO_ORE	No other Routing Engine is detected.
E_TMOUT	A request timed out.
E_NO_IPC	Routing Engine connection was lost.
E_ORE_M	Other Routing Engine state was changed to master.
E_ORE_B	Other Routing Engine state was changed to backup.
E_ORE_D	Other Routing Engine state was changed to disabled.

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