Managing Serviceguard Seventeenth Edition, First Reprint December 2009

NOTE: For a full discussion, see the white paper Serviceguard Network Manager: Inbound
Failure Detection Enhancement at http://docs.hp.com -> High Availability
-> Serviceguard -> White Papers.
• INOUT: When both the inbound and outbound counts stop incrementing for a
certain amount of time, Serviceguard will declare the card as bad. (Serviceguard
calculates the time depending on the type of LAN card.) Serviceguard will not
declare the card as bad if only the inbound or only the outbound count stops
incrementing. Both must stop. This is the default.
• INONLY_OR_INOUT: This option will also declare the card as bad if both inbound
and outbound counts stop incrementing. However, it will also declare it as bad if
only the inbound count stops.
This option is not suitable for all environments. Before choosing it, be sure these
conditions are met:
— All bridged nets in the cluster should have more than two interfaces each.
— Each primary interface should have at least one standby interface, and it should
be connected to a standby switch.
— The primary switch should be directly connected to its standby.
— There should be no single point of failure anywhere on all bridged nets.
NOTE: You can change the value of the NETWORK_FAILURE_DETECTION parameter
while the cluster is up and running.
Local Switching
A local network switch involves the detection of a local network interface failure and
a failover to the local backup LAN card (also known as the standby LAN card). The
backup LAN card must not have any IP addresses configured.
In the case of local network switch, TCP/IP connections are not lost for Ethernet, but
IEEE 802.3 connections will be lost. For IPv4, Ethernet uses the ARP protocol, and
HP-UX sends out an unsolicited ARP to notify remote systems of address mapping
between MAC (link level) addresses and IP level addresses. IEEE 802.3 does not have
the rearp function.
IPv6 uses the Neighbor Discovery Protocol (NDP) instead of ARP. The NDP protocol
is used by hosts and routers to do the following:
• determine the link-layer addresses of neighbors on the same link, and quickly
purge cached values that become invalid.
• find neighboring routers willing to forward packets on their behalf.
How the Network Manager Works 93