HP Serviceguard manual Safeguarding against Loss of Name Resolution Services

15.145.162.131 gryf.uksr.hp.com gryf

10.8.0.131 gryf2.uksr.hp.com gryf

10.8.1.131 gryf3.uksr.hp.com gryf

15.145.162.132 sly.uksr.hp.com sly

10.8.0.132 sly2.uksr.hp.com sly

10.8.1.132 sly3.uksr.hp.com sly

If applications require the use of hostname aliases, the Serviceguard hostname must be one of the aliases in all the entries for that host. For example, if the two-node cluster in the previous example were configured to use the aliases alias-node1and alias-node2, then the entries in /etc/ hosts should look something like this:

15.145.162.131 gryf.uksr.hp.com gryf alias-node1

10.8.0.131 gryf2.uksr.hp.com gryf alias-node1

10.8.1.131 gryf3.uksr.hp.com gryf alias-node1

15.145.162.132 sly.uksr.hp.com sly alias-node2

10.8.0.132 sly2.uksr.hp.com sly alias-node2

10.8.1.132 sly3.uksr.hp.com sly alias-node2

IMPORTANT: Serviceguard does not support aliases for IPv6 addresses.

For information about configuring an IPv6–only cluster, or a cluster that uses a combination of IPv6 and IPv4 addresses for the nodes' hostnames, see “About Hostname Address Families: IPv4-Only,IPv6-Only, and Mixed Mode” (page 106).

Safeguarding against Loss of Name Resolution Services

When you employ any user-level Serviceguard command (including cmviewcl), the command uses the name service you have configured (such as DNS) to obtain the addresses of all the cluster nodes. If the name service is not available, the command could hang or return an unexpected networking error message.

NOTE: If such a hang or error occurs, Serviceguard and all protected applications will continue working even though the command you issued does not. That is, only the Serviceguard configuration commands (and corresponding Serviceguard Manager functions) are affected, not the cluster daemon or package services.

The procedure that follows shows how to create a robust name-resolution configuration that will allow cluster nodes to continue communicating with one another if a name service fails. If a standby LAN is configured, this approach also allows the cluster to continue to function fully (including commands such as cmrunnode and cmruncl) after the primary LAN has failed.

Preparing Your Systems 169