How to Plan for an IPMP Group

The following procedure includes the planning tasks and information to be gathered prior to configuring the IPMP group. The tasks do not have to be performed in sequence.

1. Decide which interfaces on the system are to be part of the IPMP group.

   An IPMP group usually consists of at least two physical interfaces that are connected to the same IP link. However, you can configure a single interface IPMP group, if required. For an introduction to IPMP groups, refer to IPMP Interface Configurations. For example, you can configure the same Ethernet switch or the same IP subnet under the same IPMP group. You can configure any number of interfaces into the same IPMP group.

   You cannot use the group parameter of the ifconfig command with logical interfaces. For example, you can use the group parameter with hme0, but not with hme0:1.

2. Verify that each interface in the group has a unique MAC address.

   For instructions, refer to SPARC: How to Ensure That the MAC Address of an Interface Is Unique.

3. Choose a name for the IPMP group.

   Any non-null name is appropriate for the group. You might want to use a name that identifies the IP link to which the interfaces are attached.

4. Ensure that the same set of STREAMS modules is pushed and configured on all interfaces in the IPMP group.

   All interfaces in the same group must have the same STREAMS modules configured in the same order.

   1. Check the order of STREAMS modules on all interfaces in the prospective IPMP group.

      You can print out a list of STREAMS modules by using the ifconfig interface modlist command. For example, here is the ifconfig output for an hme0 interface:

      # ifconfig hme0 modlist 0 arp 1 ip 2 hme

      Interfaces normally exist as network drivers directly below the IP module, as shown in the output from ifconfig hme0 modlist. They should not require additional configuration.

      However, certain technologies, such as NCA or IP Filter, insert themselves as STREAMS modules between the IP module and the network driver. Problems can result in the way interfaces of the same IPMP group behave.

      If a STREAMS module is stateful, then unexpected behavior can occur on failover, even if you push the same module onto all of the interfaces in a group. However, you can use stateless STREAMS modules, provided that you push them in the same order on all interfaces in the IPMP group.

   2. Push the modules of an interface in the standard order for the IPMP group.

      ifconfig interface modinsert module-name

      ifconfig hme0 modinsert ip

5. Use the same IP addressing format on all interfaces of the IPMP group.

   If one interface is configured for IPv4, then all interfaces of the group must be configured for IPv4. Suppose you have an IPMP group that is composed of interfaces from several NICs. If you add IPv6 addressing to the interfaces of one NIC, then all interfaces in the IPMP group must be configured for IPv6 support.

6. Check that all interfaces in the IPMP group are connected to the same IP link.

7. Verify that the IPMP group does not contain interfaces with different network media types.

   The interfaces that are grouped together should be of the same interface type, as defined in /usr/include/net/if_types.h. For example, you cannot combine Ethernet and Token ring interfaces in an IPMP group. As another example, you cannot combine a Token bus interface with asynchronous transfer mode (ATM) interfaces in the same IPMP group.

8. For IPMP with ATM interfaces, configure the ATM interfaces in LAN emulation mode.

   IPMP is not supported for interfaces using Classical IP over ATM.