Managing Serviceguard 14th Edition, June 2007

Understanding Serviceguard Software Components
How the Network Manager Works
Chapter 3 101
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.
• actively keep track of which neighbors are reachable, and which are
not, and detect changed link-layer addresses.
• search for alternate functioning routers when the path to a router
fails.