Management IP failover

If the configuration node fails, the IP addresses for the clustered system are transferred to a new node. The system services are used to manage the transfer of the management IP addresses from the failed configuration node to the new configuration node.

The following changes are performed by the system service:

If software on the failed configuration node is still operational, the software shuts down the management IP interfaces. If the software cannot shut down the management IP interfaces, the hardware service forces the node to shut down.
When the management IP interfaces shut down, all remaining nodes choose a new node to host the configuration interfaces.
The new configuration initializes the configuration daemons, including SSHD and HTTPD, and then binds the management IP interfaces to its Ethernet ports.
The router is configured as the default gateway for the new configuration.
The routing tables are established on the new configuration for the management IP addresses. The new configuration sends five unsolicited address resolution protocol (ARP) packets for each IP address to the local subnet broadcast address. The ARP packets contain the management IP and the Media Access Control (MAC) address for the new configuration node. All systems that receive ARP packets are forced to update their ARP tables. After the ARP tables are updated, these systems can connect to the new configuration node.
Note: Some Ethernet devices might not forward ARP packets. If the ARP packets are not forwarded, connectivity to the new configuration node cannot be established automatically. To avoid this problem, configure all Ethernet devices to pass unsolicited ARP packets. You can restore lost connectivity by logging in to the system and starting a secure copy to the affected system. Starting a secure copy forces an update to the ARP cache for all systems that are connected to the same switch as the affected system.

Ethernet link failures

If the Ethernet link to the system fails because of an event that is unrelated to the system , the system does not attempt to fail over the configuration node to restore management IP access. For example, the Ethernet link can fail if a cable is disconnected or an Ethernet router fails. To protect against this type of failure, the system provides the option for two Ethernet ports that each have a management IP address. If you cannot connect through one IP address, attempt to access the system through the alternative IP address.

Note: IP addresses that are used by hosts to access the system over an Ethernet connection are different from management IP addresses.

Note: IP addresses that are used by hosts to access the system over iSCSI are different from management IP addresses.

Routing considerations for event notification and Network Time Protocol

The system supports the following protocols that make outbound connections:

Email
Simple Network Mail Protocol (SNMP)
Syslog
Network Time Protocol (NTP)
Lightweight Directory Access Protocol (LDAP)

These protocols operate only on a port that is configured with a management IP address. When it is making outbound connections, the system uses the following routing decisions:

If the destination IP address is in the same subnet as one of the management IP addresses, the system sends the packet immediately.
If the destination IP address is not in the same subnet as either of the management IP addresses, the system sends the packet to the default gateway for Ethernet port 1.
If the destination IP address is not in the same subnet as either of the management IP addresses and Ethernet port 1 is not connected to the Ethernet network, the system sends the packet to the default gateway for Ethernet port 2.

When you configure any of these protocols for event notifications, use these routing decisions to ensure that error notification works correctly if the network fails.