HP Serviceguard manual Monitoring LAN Interfaces and Detecting Failure Link Level, Load Sharing

IP addresses are configured only on each primary network interface card; standby cards are not configured with an IP address. Multiple IPv4 addresses on the same network card must belong to the same IP subnet.

CAUTION: HP strongly recommends that you add relocatable addresses to packages only by editing ip_address (page 243) in the package configuration file (or IP [] entries in the control script of a legacy package) and running cmapplyconf (1m).

Load Sharing

Serviceguard allows you to configure several services into a single package, sharing a single IP address; in that case all those services will fail over when the package does. If you want to be able to load-balance services (that is, move a specific service to a less loaded system when necessary) you can do so by putting each service in its own package and giving it a unique IP address.

Monitoring LAN Interfaces and Detecting Failure: Link Level

At regular intervals, determined by the NETWORK_POLLING_INTERVAL (see “Cluster Configuration Parameters ” (page 109)) Serviceguard polls all the network interface cards specified in the cluster configuration file. Network failures are detected within each single node in the following manner. One interface on the node is assigned to be the poller. The poller will poll the other primary and standby interfaces in the same bridged net on that node to see whether they are still healthy.

Normally, the poller is a standby interface; if there are no standby interfaces in a bridged net, the primary interface is assigned the polling task. (Bridged nets are explained under “Redundant Network Components ” (page 28) in Chapter 2.)

The polling interface sends LAN packets to all other interfaces in the node that are on the same bridged net and receives packets back from them.

Whenever a LAN driver reports an error, Serviceguard immediately declares that the card is bad and performs a local switch, if applicable. For example, when the card fails to send, Serviceguard will immediately receive an error notification and it will mark the card as down. See “Reporting Link-Level and IP-Level Failures” (page 76).

Serviceguard Network Manager also looks at the numerical counts of packets sent and received on an interface to determine if a card is having a problem. There are two ways Serviceguard can handle the counts of packets sent and received. In the cluster configuration file, choose one of the following values for the NETWORK_FAILURE_DETECTION parameter:

NOTE: For a full discussion, see the white paper Serviceguard Network Manager: Inbound Failure Detection Enhancement at http://www.hp.com/go/hpux-serviceguard-docs.

•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.

How the Network Manager Works 69