Learning OpenStack Networking - Third Edition

Attaching multiple interfaces

By passing the --nic argument multiple times, it is possible to attach multiple interfaces to an instance. The interfaces within the instance may then be enumerated as eth0, eth1, eth2, and so on, depending on the operating system.

Attaching multiple network interfaces to an instance is referred to as multihoming. When an instance is multihomed, neither Neutron nor the instance itself is aware of which network takes precedence over another. When attached networks and subnets have their own respective gateway addresses set, an instance's routing table can be populated with multiple default routes. This scenario can wreak havoc on the connectivity and routing behavior of an instance. This configuration is useful ...