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System Administration Guide: Network Interfaces and Network Virtualization

ProcedureHow to Plan an IPMP Group

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

  1. Determine the general IPMP configuration that would suit your needs.

    Your IPMP configuration depends on what your network needs to handle the type of traffic that is hosted on your system. IPMP spreads outbound network packets across the IPMP group's interfaces, and thus improves network throughput. However, for a given TCP connection, inbound traffic normally follows only one physical path to minimize the risk of processing out-of-order packets.

    Thus, if your network handles a huge volume of outbound traffic, configuring multiple interfaces into an IPMP group can improve network performance. If instead, the system hosts heavy inbound traffic, then the number of interfaces in the group does not necessarily improve performance by load spreading traffic. However, having multiple interfaces helps to guarantee network availability during interfaces failure.

  2. For SPARC based systems, verify that each interface in the group has a unique MAC address.

    To configure a unique MAC address for each interface in the system, see SPARC: How to Ensure That the MAC Address of an Interface Is Unique.

  3. 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 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 insert themselves as a STREAMS module between the IP module and the network driver. 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@position


      ifconfig hme0 modinsert vpnmod@3

  4. 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. For example, if you add IPv6 addressing to one interface, then all interfaces in the IPMP group must be configured for IPv6 support.

  5. Determine the type of failure detection that you want to implement.

    For example, if you want to implement probe-based failure detection, then you must configure test addresses on the underlying interfaces. For related information, seeTypes of Failure Detection in IPMP.

  6. Ensure that all interfaces in the IPMP group are connected to the same local network.

    For example, you can configure Ethernet switches on the same IP subnet into an IPMP group. You can configure any number of interfaces into an IPMP group.

    Note –

    You can also configure a single interface IPMP group, for example, if your system has only one physical interface. For related information, see Types of IPMP Interface Configurations.

  7. Ensure 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.