System Administration Guide: IP Services

IPMP Interface Configurations

An IPMP configuration typically consists of two or more physical interfaces on the same system that are attached to the same IP link. These physical interfaces might or might not be on the same NIC. The interfaces are configured as members of the same IPMP group. If the system has additional interfaces on a second IP link, you must configure these interfaces as another IPMP group.

A single interface can be configured in its own IPMP group. The single interface IPMP group has the same behavior as an IPMP group with multiple interfaces. However, failover and failback cannot occur for an IPMP group with only one interface.

You can also configure VLANs into an IPMP group by using the same steps to configure a group out of IP interfaces. For the procedures, see Configuring IPMP Groups. The same requirements that are listed in Basic Requirements of IPMP apply to configure VLANs into an IPMP group.

Caution – Caution –

The convention that is used to name VLANs might lead to errors when you configure VLANs as an IPMP group. For more details about VLAN names, see VLAN Tags and Physical Points of Attachment in System Administration Guide: IP Services. Consider the example of four VLANs, bge1000, bge1001, bge2000, and bge2001. IPMP implementation requires these VLANs to be grouped as follows: bge1000 and bge1001 belong to one group on the same VLAN 1, while bge2000, and bge2001 belong to another group on the same VLAN 2. Because of VLAN names, errors such as mixing VLANs that belong to different links into an IPMP group can easily occur, for example, bge1000 and bge2000.

Standby Interfaces in an IPMP Group

The standby interface in an IPMP group is not used for data traffic unless some other interface in the group fails. When a failure occurs, the data addresses on the failed interface migrate to the standby interface. Then, the standby interface is treated the same as other active interfaces until the failed interface is repaired. Some failovers might not choose a standby interface. Instead, these failovers might choose an active interface with fewer data addresses that are configured as UP than the standby interface.

You should configure only test addresses on a standby interface. IPMP does not permit you to add a data address to an interface that is configured through the ifconfig command as standby. Any attempt to create this type of configuration will fail. Similarly, if you configure as standby an interface that already has data addresses, these addresses automatically fail over to another interface in the IPMP group. Due to these restrictions, you must use the ifconfig command to mark any test addresses as deprecated and -failover prior to setting the interface as standby. To configure standby interfaces, refer to How to Configure a Standby Interface for an IPMP Group.

Common IPMP Interface Configurations

As mentioned in IPMP Addressing, interfaces in an IPMP group handle regular data traffic and probe traffic, depending on the interfaces' configuration. You use IPMP options of the ifconfig command to create the configuration.

An active interface is a physical interface that transmits both data traffic and probe traffic. You configure the interface as “active” by performing either the task How to Configure an IPMP Group With Multiple Interfaces or the task How to Configure a Single Interface IPMP Group.

The following are two common types of IPMP configurations:

Active-active configuration

A two interface IPMP group where both interfaces are “active,” that is they might be transmitting both probe and data traffic at all times.

Active-standby configuration

A two interface IPMP group where one interface is configured as “standby.”

Checking the Status of an Interface

You can check the status of an interface by issuing the ifconfig interface command. For general information on ifconfig status reporting, refer to How to Get Information About a Specific Interface.

For example, you can use the ifconfig command to obtain the status of a standby interface. When the standby interface is not hosting any data address, the interface has the INACTIVE flag for its status. You can observe this flag in the status lines for the interface in the ifconfig output.