Managing Serviceguard Sixteenth Edition, March 2009

SUBNET 192.168.3.0
IP_MONITOR OFF
NOTE: This is the default if cmquerycl does not detect a gateway for the subnet in
question; it is equivalent to having no SUBNET entry for the subnet. See SUBNET under
“Cluster Configuration Parameters ” (page 138) for more information.
Constraints and Limitations
• A subnet must be configured into the cluster in order to be monitored.
• Polling targets are not detected beyond the first-level router.
• Polling targets must accept and respond to ICMP (or ICMPv6) ECHO messages.
• A peer IP on the same subnet should not be a polling target because a node can
always ping itself.
• On an HP-UX system, an IP-level failure on the standby interface will not be
detected until the IP address fails over to the standby.
• On an HP-UX system, after the IP address fails over to the standby, the IP monitor
will not detect recovery on the primary interface.
The following constraints apply to peer polling when there are only two interfaces on
a subnet:
• If one interface fails, both interfaces and the entire subnet will be marked down
on each node, unless Local Switching (page 94) is configured and there is a working
standby.
• If the node that has one of the interfaces goes down, the subnet on the other node
will be marked down.
Reporting Link-Level and IP-Level Failures
Serviceguard detects both link-level and IP-level failures; see “Monitoring LAN
Interfaces and Detecting Failure: Link Level” (page 93) and “Monitoring LAN Interfaces
and Detecting Failure: IP Level” (page 99) for information about each level of
monitoring. Any given failure may occur at the link level or the IP level. In addition,
local switching may occur, that is, a switch to a standby LAN card if one has been
configured; see “Local Switching ” (page 94).
The following examples show when and how a link-level failure is differentiated from
an IP-level failure in the output of cmviewcl (1m).
As you can see, if local switching is configured, the difference is the keyword disabled,
which appears in the tabular output, and is set to true in the line output, if the IP
Monitor detects the failure. If local switching is not configured, the output is the same
whether link-level or IP monitoring detects the failure.
102 Understanding Serviceguard Software Components