System Administration Guide: Network Interfaces and Network Virtualization

IPMP and Dynamic Reconfiguration

Dynamic reconfiguration (DR) feature allows you to reconfigure system hardware, such as interfaces, while the system is running. DR can be used only on systems that support this feature.

You typically use the cfgadm command to perform DR operations. However, some platforms provide other methods. Make sure to consult your platform's documentation for details to perform DR. For systems that use the Solaris OS, you can find specific documentation about DR in the resources that are listed in Table 7–1. Current information about DR is also available at and can be obtained by searching for the topic “dynamic reconfiguration.”

Table 7–1 Documentation Resources for Dynamic Reconfiguration


For Information 

Detailed information on the cfgadm command

cfgadm(1M) man page

Specific information about DR in the Sun Cluster environment 

Sun Cluster 3.1 System Administration Guide

Specific information about DR in the Sun Fire environment 

Sun Fire 880 Dynamic Reconfiguration Guide

Introductory information about DR and the cfgadm command

Chapter 6, Dynamically Configuring Devices (Tasks), in System Administration Guide: Devices and File Systems

Tasks for administering IPMP groups on a system that supports DR 

Recovering an IPMP Configuration With Dynamic Reconfiguration

The sections that follow explain how DR interoperates with IPMP.

On a system that supports DR of NICs, IPMP can be used to preserve connectivity and prevent disruption of existing connections. IPMP is integrated into the Reconfiguration Coordination Manager (RCM) framework. Thus, you can safely attach, detach, or reattach NICs and RCM manages the dynamic reconfiguration of system components.

Attaching New NICs

With DR support, you can attach, plumb, and then add new interfaces to existing IPMP groups. Or, if appropriate, you can configure the newly added interfaces into their own IPMP group. For procedures to configure IPMP groups, refer to Configuring IPMP Groups. After these interfaces have been configured, they are immediately available for use by IPMP. However, to benefit from the advantages of using customized link names, you must assign generic link names to replace the interface's hardware-based link names. Then you create corresponding configuration files by using the generic name that you just assigned. For procedures to configure a singe interface by using customized link names, refer to How to Configure an IP Interface After System Installation. After you assign a generic link name to interface, make sure that you always refer to the generic name when you perform any additional configuration on the interface such as using the interface for IPMP.

Detaching NICs

All requests to detach system components that contain NICs are first checked to ensure that connectivity can be preserved. For instance, by default you cannot detach a NIC that is not in an IPMP group. You also cannot detach a NIC that contains the only functioning interfaces in an IPMP group. However, if you must remove the system component, you can override this behavior by using the -f option of cfgadm, as explained in the cfgadm(1M) man page.

If the checks are successful, the daemon sets the OFFLINE flag for the interface. All test addresses on the interfaces are unconfigured. Then, the NIC is unplumbed from the system. If any of these steps fail, or if the DR of other hardware on the same system component fails, then the previous configuration is restored to its original state. A status message about this event will be displayed. Otherwise, the detach request completes successfully. You can remove the component from the system. No existing connections are disrupted.

Replacing NICs

When an underlying interface of an IPMP group fails, a typical solution would be to replace the failed interface by attaching a new NIC. RCM records the configuration information associated with any NIC that is detached from a running system. If you replace a failed NIC with an identical NIC, then RCM automatically configures the interface according to the contents of the existing /etc/hostname.interface file.

For example, suppose you replace a failed bge0 interface with another bge0 interface. The failed bge0 already has a corresponding /etc/hostname.bge0 file. After you attach the replacement bge NIC, RCM plumbs and then configures the bge0 interface by using the information in the /etc/hostname.bge0 file. Thus the interface is properly configured with the test address and is added to the IPMP group according to the contents of the configuration file.

You can replace a failed NIC with a different NIC, provided that both are the same type, such as ethernet. In this case, RCM plumbs the new interface after it is attached. If you did not use customized link names when you first configured your interfaces, and no corresponding configuration file for the new interface exists, then you will have to perform additional configuration steps. You will need to create a new corresponding configuration file for the new NIC. Additionally, you will need to add correct information to the file before you can add the interface to the IPMP group.

However, if you used customized link names, the additional configuration steps are unnecessary. By reassigning the failed interface's link name to the new interface, then the new interface acquires the configuration specified in the removed interface's configuration file. RCM then configures the interface by using the information in that file. For procedures to recover your IPMP configuration by using DR when an interface fails, refer to Recovering an IPMP Configuration With Dynamic Reconfiguration.