Managing HP Serviceguard A.11.20.00 for Linux, June 2012

Figure 25 Bonded NICs Configured for Load Balancing
Monitoring LAN Interfaces and Detecting Failure: Link Level
At regular intervals, determined by the NETWORK_POLLING_INTERVAL (see “Cluster Configuration
Parameters ” (page 80)), Serviceguard polls all the network interface cards specified in the cluster
configuration file (both bonded and non-bonded). If the link status of an interface is down,
Serviceguard marks the interface, and all subnets running on it, as down; this is shown in the output
of cmviewcl (1m); see “Reporting Link-Level and IP-Level Failures” (page 61). When the link
comes back up, Serviceguard marks the interface, and all subnets running on it, as up.
Monitoring LAN Interfaces and Detecting Failure: IP Level
Serviceguard can also monitor the IP level, checking Layer 3 health and connectivity for both IPv4
and IPv6 subnets. This is done by the IP Monitor, which is configurable: you can enable IP monitoring
for any subnet configured into the cluster, but you do not have to monitor any. You can configure
IP monitoring for a subnet, or turn off monitoring, while the cluster is running.
The IP Monitor:
• Detects when a network interface fails to send or receive IP messages, even though it is still
up at the link level.
• Handles the failure, failover, recovery, and failback.
Reasons To Use IP Monitoring
Beyond the capabilities already provided by link-level monitoring, IP monitoring can:
• Monitor network status beyond the first level of switches; see “How the IP Monitor Works”
(page 59)
• Detect and handle errors such as:
IP packet corruption on the router or switch◦
◦ Link failure between switches and a first-level router
58 Understanding Serviceguard Software Components