Another use for multiple network interfaces is to provide a backup in case of network failure. If a client is connected to a server via two networks, the client can establish a connection via the second network if the first one goes down.
To configure an instance for query port backup:
Install multiple “master” and “query” lines in a server entry in the interfaces file.
An instance listens for connections at both ports. Clients looking for a host name and a port number for a connection to an instance try the port on each “query” line in order, until they establish a connection.
The following example shows how to configure a backup network that will be used only if the normal connection fails. The primary network is “corporate network” and backup is “engineering network.”
# PRODUCTION server with two network listeners PRODUCTION<tab>3<tab>3<newline> <tab>master tcp ether SERV_CORPNET 4559 <tab>master tcp ether SERV_ENGNET 5479 <tab>query tcp ether SERV_CORPNET 4559 <tab>query tcp ether SERV_ENGNET 5479
Configure PC-client interfaces files with the appropriate multiple “query” entries, as described in the Open Client documentation. For client interfaces files in a homogeneous environment, you can copy the entire interfaces file entry for the instance into the client interfaces file.
A connection on the secondary port occurs only if the corporate network is disabled, or if the corporate network interface on the host machine fails or is shut down due to a network-related failure.
