Virtual IP failover

Through the virtual IP failover feature, Content Gateway maintains a pool of virtual IP addresses that it assigns to the nodes in the cluster as necessary. These addresses are virtual only in the sense that they are not tied to a specific machine; Content Gateway can assign them to any of its nodes. To the outside world, these virtual IP addresses are the addresses of Content Gateway servers.

Virtual IP failover assures that if a node in the cluster fails, other nodes can assume the failed node's responsibilities. Content Gateway handles virtual IP failover in the following ways:

The content_manager process maintains cluster communication. Nodes automatically exchange statistics and configuration information through multicast communication. If multicast heartbeats are not received from one of the cluster nodes, the other nodes recognize it as unavailable.

The content_manager process reassigns the IP addresses of the failed node to the remaining operational nodes within approximately 30 seconds, so that service can continue without interruption.

The IP addresses are assigned to new network interfaces, and the new assignment is broadcast to the local network. The IP address reassignment is done through a process called ARP rebinding.

What are virtual IP addresses?

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Related topics:

Enabling and disabling virtual IP addressing

Adding and editing virtual IP addresses

Virtual IP addresses are IP addresses that are not tethered to particular machines. Thus, they can rotate among nodes in a Content Gateway cluster.

It is common for a single machine to represent multiple IP addresses on the same subnet. This machine would have a primary or real IP address bound to its interface card and also serve many more virtual addresses.

You can set up your user base to use a DNS round-robin pointing at virtual IP addresses, as opposed to using the real IP addresses of the Content Gateway machines.

Because virtual IP addresses are not bound to machines, a Content Gateway cluster can take addresses from inactive nodes and distribute those addresses among the remaining live nodes.

Using a proprietary management protocol, Content Gateway nodes communicate their status with their peers. If a node fails, its peers notice the failure and negotiate which of the remaining nodes will mask the fault by taking over the failed node's virtual interface.