Logical Domains with IPMP

IP Multipathing (IPMP) is a way to bring redundancy into your Solaris networking. In essence, you can connect one physical, or, in this case, virtual server to multiple switches. In the event that one network interface should go down, then the server will still be accessible over the network. The idea is that you take two or more interfaces and make them part of an interface group. You assign an IP to one or both of those interfaces. In the event of a link failure on one interface, the other interface in the group continues to advertise the IP of the other. For a full explanation of IPMP, see the Oracle Solaris System Administration Guide : IP Services

There are two types of IPMP, Link based and Probe based, and both can be set up as either active/active or active/standby. You can use either for physical servers, but for LDOM's, you can only use Probe based IPMP. In Probe based IPMP, one or more of the interfaces are given a real IP which the server can use for external communication. Each interface in the IPMP group also has a virtual interface assigned to it which is given a test IP. The test IP is used to probe the network, by sending out ICMP ping packets on the virtual test interface, to either manually specified or automatically generated targets. In the event that one of the test IP's fails in it's probing, then that interface is marked as failed, and then one of the other interfaces in the IPMP group picks up the 'real' IP.

In the sample 'ifconfig' output below, you can see there are two interface, vnet0 and vnet1. vnet0 has the external IP of 10.10.10.40 and the test IP of 10.10.10.42 on it's virtual interface, vnet0:1. vnet1 has the dummy IP 0.0.0.0, as we only want to use one external IP for data. However, vnet1 has a test IP assigned on vnet1:1 of 10.10.10.43.

 vnet0: flags=201000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> mtu 1500 index 2
         inet 10.10.10.40 netmask fffffc00 broadcast 10.203.167.255
         groupname vtn-mgmt
         ether 0:14:4f:fa:a2:6b
 vnet0:1: flags=209040843<UP,BROADCAST,RUNNING,MULTICAST,DEPRECATED,IPv4,NOFAILOVER,CoS> mtu 1500 index 2
         inet 10.10.10.42 netmask fffffc00 broadcast 10.203.167.255
 vnet1: flags=201000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> mtu 1500 index 3
         inet 0.0.0.0 netmask ff000000 broadcast 0.255.255.255
         groupname vtn-mgmt
         ether 0:14:4f:fa:87:50
 vnet01:1: flags=209040843<UP,BROADCAST,RUNNING,MULTICAST,DEPRECATED,IPv4,NOFAILOVER,CoS> mtu 1500 index 3
         inet 10.10.10.43 netmask fffffc00 broadcast 10.203.167.255