Managing Serviceguard Eighteenth Edition, September 2010

NOTE: This applies only to subnets for which the cluster configuration
parameter IP_MONITOR is set to ON. See “Cluster Configuration Parameters
” (page 143) for more information.
— Errors that prevent packets from being received but do not affect the link-level
health of an interface
IMPORTANT: You should configure the IP Monitor in a cross-subnet configuration,
because IP monitoring will detect some errors that link-level monitoring will not. See
also “Cross-Subnet Configurations” (page 41).
How the IP Monitor Works
Using Internet Control Message Protocol (ICMP) and ICMPv6, the IP Monitor sends
polling messages to target IP addresses and verifies that responses are received. When
the IP Monitor detects a failure, it marks the network interface down at the IP level, as
shown in the output of cmviewcl (1m). If there is a standby, the subnet is failed over
to the standby. See “Reporting Link-Level and IP-Level Failures” (page 101) and “Failure
and Recovery Detection Times” (page 101).
The monitor can perform two types of polling:
• Peer polling.
In this case the IP Monitor sends ICMP ECHO messages from each IP address on
a subnet to all other IP addresses on the same subnet on other nodes in the cluster.
• Target polling.
In this case the IP Monitor sends ICMP ECHO messages from each IP address on
a subnet to an external IP address specified in the cluster configuration file; see
POLLING_TARGET under “Cluster Configuration Parameters ” (page 143).
cmquerycl (1m) will detect gateways available for use as polling targets, as
shown in the example below.
Target polling enables monitoring beyond the first level of switches, allowing you
to detect if the route is broken anywhere between each monitored IP address and
the target.
NOTE: In a cross-subnet configuration, nodes can configure peer interfaces on
nodes on the other routed subnet as polling targets.
HP recommends that you configure target polling if the subnet is not private to the
cluster.
The IP Monitor section of the cmquerycl output looks similar to this:
…
Route Connectivity (no probing was performed):
How the Network Manager Works 99