3.1. Configuring Multi-Homed Hosts

By default, UM will select the first multicast-capable, non-loopback interface for multicast topic resolution. If you are fortunate, on a multi-homed host, the correct interface will be selected. However, this fortuitous selection should not be relied upon. Moving the interface card to a different slot, a change in the operating system kernel, and numerous other factors can lead to a different ordering of interfaces as reported by the operating system. This in turn can lead UM to a select a different interface after the change.

It is strongly recommended that the actual interface be specified. The resolver_multicast_interface option allows you to explicitly specify the multicast interface. Note that this also changes the interface for LBT-RM and multicast immediate messaging.

Other options of interest include resolver_unicast_interface when using the unicast resolver, request_tcp_interface when using the request/response messaging, transport_lbtru_interface and transport_tcp_interface for receivers, and transport_lbtru_interface and transport_tcp_interface for sources, depending on the transport being used.