Less known Solaris features - IP Multipathing (Part 7): New IPMP and link aggregation
As I wrote before there is another way to protect your system against the failure of a network connection - Link Aggregation. As i’ve explained before, there are failure modes that can’t be addressed by link aggregation. But you can use both in conjunction. This makes sense, when your main connection is a 10GBe interface and you don’t want to plug a second one into the system and use already existent 1GBe Interfaces as a backup for it instead.
It’s pretty straightforward to do so. At first you have to configure the link aggregation.
The dladm create-aggr creates an aggregation, that bundles the interfaces e1000g0 and e1000g1 into a single virtual interface. Now I plug both cables into the switch.
Interfaces are up, the aggregation is ready for use.
Looks pretty much like a standard IPMP configuration. You can think of aggregate0 as a plain-standard physical interface from the perspective the the admin. When we check the IPMP configuration we will see both interfaces.
Now we unplug one of the aggregated cables.
Everything is still okay. The aggregate hides the fact of the one failed interface from the IPMP subsystem. Now we unplug the second interface.
The links are both down, and without a functional interface left, the “link” of the aggregate goes down as well (It stays up, as long as there’s a functional interface in the aggregate). Of course the IPMP subsystem switches to rge0 now. When we plug one cable back to the switch, the aggregate is functional again and IPMP detects this and the interface is considered as functional in IPMP again, too.
When you plug the second interface into the interface, the aggregate is complete. But it doesn’t change a thing from the IPMP side, as the aggregate0 interface was already functional from the perpective of IPMP with just one interface.