Etherchannel on the fly
Some time ago I provided an elaborate method of Building a channel under the SEA. It explained how to increase the bandwidth of an etherchannel, using the failover mechanism of the Shared Ethernet Adapter (the “SEA”) to make the change. I suggested you remove the non-active SEA so you could add some more adapters to an etherchannel (link aggregation). Once the etherchannel was rebuilt, you could reinstate your SEA configuration and do the same change on the other SEA.
I have since discovered that I was being
too clever by half
Although the procedure I suggested was perfectly legitimate, it was also perfectly unnecessary. You can add an adapter to an etherchannel configuration while it’s in use. Even if the etherchannel is holding a great big grunty SEA above its head.
Change that channel!
In the following example, there is an etherchannel (ent2) which is made up of three ports: ent0,ent1 and ent6. As you can see the parent adapter is the Shared Ethernet Adapter (ent5). To add an extra port (ent7) to the etherchannel configuration, you can select it using “Add Main Adapter”.
Of course, you need to have the switch port configured as part of the trunk. You can use the entstat command on the VIO server command line (logged in as padmin) to view the active adapters.
I ran entstat –all ent5 and looked for Link. When the cabling and switch configuration is right, the Link should change from UNKNOWN to Up.
A SEA of cables
The ability to add or delete adapters belonging to an etherchannel on the fly means you can easily move cables around if you need to. It will even work if you don’t have an SEA failover configuration, such as when you only have a single VIO Server.
This online change to etherchannel came out with AIX 5.2 Maintenance Level 1, way back in 2002. No, I wasn't waiting for the technology to mature. It just took me eight years to notice.