If the configuration node fails, the IP addresses for the 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.
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).
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 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.