Installation guide

Figure 1.5. LVS Components

The pulse daemon runs on both the active and passive LVS routers. On the backup router,

pulse sends a heartbeat to the public interface of the active router to make sure the active

router is still properly functioning. On the active router, pulse starts the lvs daemon and

responds to heartbeat queries from the backup LVS router.

Once started, the lvs daemon calls the ipvsadm utility to configure and maintain the IPVS

routing table in the kernel and starts a nanny process for each configured virtual server on each

real server. Each nanny process checks the state of one configured service on one real server,

and tells the lvs daemon if the service on that real server is malfunctioning. If a malfunction is

detected, the lvs daemon instructs ipvsadm to remove that real server from the IPVS routing

table.

If the backup router does not receive a response from the active router, it initiates failover by

calling send_arp to reassign all virtual IP addresses to the NIC hardware addresses (MAC

address) of the backup node, sends a command to the active router via both the public and

private network interfaces to shut down the lvs daemon on the active router, and starts the lvs

daemon on the backup node to accept requests for the configured virtual servers.

LVS Components