By hovering the mouse pointer over the "Failover VIP" button a message will be displayed that will explain why it is disabled.
The possible reasons are:
- Cluster VIPs in transition - No VIPs are owned by any of the cluster nodes, the cluster is deciding which node should host the VIPs.
- Disconnected Gateway or Interface - Either the cluster node is not getting a response to an ARP request from the interface gateway or the interface link is down, so do not allow failover.
- Cluster in transition - Cluster is transitioning so do not allow failover.
- Failover in progress - Failover to the passive node is in progress
- Disabled or Unreachable Node State - Cluster is disabled on this node or the peer node is unreachable.
- Peer Unreachable or Partitioned - Peer node is unreachable or there is a problem with the group communication subsystem.
For internal interfaces, if the ARP for the gateway fails then the interface is marked down. As cluster communication occurs over the internal interfaces this can lead to a split cluster as both devices would then advertise the VIP, each believing they are the Active member. To avoid this situation enable
Disable external interface when internal interface fails at
System >
Clustering >
Cluster Properties.KB21584 - Cluster VIP flapping between both of the nodes in Active/Passive cluster describes what happens if both devices cannot resolve their internal gateways.
If the external interface on the Active node cannot resolve the ARP for the external gateway address then VIP fail-over proceeds.
If the external interface on the Passive node cannot resolve the ARP for the external gateway address then the VIP fail-over button greys out and displays 'Disconnected device or gateway."
