Managing HP Serviceguard A.11.20.00 for Linux, June 2012

◦ Inbound failures
◦ 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 23).
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); see “Reporting Link-Level and IP-Level Failures” (page 61) and “Failure and Recovery Detection
Times” (page 60).
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 80). 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):
IPv4:
1 16.89.143.192
16.89.120.0
…
Possible IP Monitor Subnets:
IPv4:
16.89.112.0 Polling Target 16.89.112.1
IPv6:
3ffe:1000:0:a801:: Polling Target 3ffe:1000:0:a801::254
…
The IP Monitor section of the cluster configuration file will look similar to the following for a subnet
on which IP monitoring is configured with target polling.
How the Network Manager Works 59