Document ID: 15060
Cisco has announced the end-of-sale for the Cisco LocalDirector. For more information, refer to the LocalDirector 400 Series End-of-Life and End-of-Sale Notices and Product Bulletins.
Contents
Introduction
The information in this Tech Note applies to all hardware and software versions of the Cisco LocalDirector in a failover configuration.
Two types of failover can be implemented in LocalDirector: standard failover and statefull failover. In standard (non-statefull) failover, all existing connection information is lost upon failover; however, statefull failover maintains session information, as well as sticky session information.
Failover Commands
- failover ip address ip_address - Sets the failover IP address. The ip_address argument indicates the IP address used by the standby unit to communicate with the active unit. Use this IP address with the ping command to check the status of the standby unit. This address must be on the same network as the system IP address. For example, if the system IP address is 192.168.1.1, set the failover IP address to 192.168.1.2.
- failover [active] - Enables access to the optional failover feature. The optional active argument makes a LocalDirector the active unit.
- replicate interface interface_number - Enables statefull failover, and specifies an interface for sending replication data. The interface_number argument indicates the number through which the active LocalDirector unit sends connection replication data to the standby unit. The default is interface 0.
- failover alias ip address ip_address - Assigns a failover alias IP address. The IP address is used by the standby unit to communicate with the active unit.
- failover reset - Takes a unit out of the failed state
- show failover - Shows LocalDirector failover status, cable status, primary and secondary host status, and interface descriptions.
- shutdown ethernet | fddi interface_number - Disables an interface.
For more information, see The LocalDirector Command Reference.
Configurations
Below is a basic configuration of LocalDirector in standard failover.
Below is a sample configuration of LocalDirector in statefull failover. Statefull failover units share connection information for active connections and are configurable on a per-virtual basis. Each time the state of the Transmission Control Protocol (TCP) connection changes, the data is sent to the standby LocalDirector via LocalDirector-statefull protocol. This allows the current state of all the TCP sessions to be mirrored to the standby LocalDirector.
LocalDirector-statefull protocol uses User Datagram Protocol (UDP) packets to send the state changes to the Standby LocalDirector over the Ethernet interface. Use a separate Ethernet interface to send statefull failover messages. With statefull failover, there is no interruption of service to client. It is ideal for mission-critical applications and allows for high availability.
Note: This example uses interface Ethernet 2, which has a crossover between the two LocalDirectors to transfer state information. This example also uses the following replicate commands:
replicate interface 2 replicate 10.1.1.5:0:0:tcp
These commands tell LocalDirector to replicate the connection state from active to standby units across Ethernet 2 and also to replicate all state information from the virtual 10.1.1.5 to the standby unit.
Note: All interfaces initially are in waiting mode, meaning that network monitoring has not started. After network interfaces go into normal mode, network monitoring begins. This happens when LocalDirector-HELLO messages begin sending every five seconds.
If a 30-second interval passes with no LocalDirector-HELLO messages being received, units go into testing mode to determine which unit failed. If the serial cable is pulled, units will maintain their current role. If the unit does not pass a test, it will become failed and the other unit will become active. Every time the ?state? of the TCP connection changes, data is sent to the standby LocalDirector via LocalDirector-statefull protocol. The state of all the TCP sessions is mirrored to the Standby LocalDirector. If a virtual is changed to support statefull failover then state information for only the new connections is sent to the standby LocalDirector. LocalDirector statefull protocol does not copy the state of existing TCP sessions.
Verifying Failover Status
The show failover command can be used to display the current failover status of the units and their interfaces, as shown in the example below.
Failover Off
Cable status: My side not connected
This host: Secondary - Active
Active time: 1 weeks, 3 days, 1 hours, 2 minutes, 5 seconds
Interface 5 (10.86.16.225): Normal (Waiting)
Interface 4 (10.86.16.225): Normal (Waiting)
Interface 3 (10.86.16.225): Normal (Administratively down)
Interface 2 (10.86.16.225): Normal (Administratively down)
Interface 1 (10.86.16.225): Normal (Waiting)
Interface 0 (10.86.16.225): Normal (Waiting)
Other host: Secondary - Standby
Interface 5 (0.0.0.0): Normal (Waiting)
Interface 4 (0.0.0.0): Normal (Waiting)
Interface 3 (0.0.0.0): Normal (Administratively down)
Interface 2 (0.0.0.0): Normal (Administratively down)
Interface 1 (0.0.0.0): Normal (Waiting)
Interface 0 (0.0.0.0): Normal (Waiting) This shows that hello packets are being passed back and forth between the two units and that two of the interafaces on the LDs have been shut down.
Related Information
| Updated: Jan 31, 2006 | Document ID: 15060 |