Link-based IPMP setup with VCS

With Solaris 10 came a nice feature – Link-based IP Multipathing (IPMP). It determines NIC availability solely on the NIC driver reporting the physical link status – UP or DOWN. Previous versions used “probe-based” IPMP, where connectivity is tested by pinging something on the network from each interface. While probe-based is actually a more thorough test (tests network layer 3 as well as 2), it is much more cumbersome to configure, and you need an extra IP address for each interface for “test” addresses. IMO Link-based IPMP is sufficient for most applications.

For some reason, configuring link-based IPMP in VCS is somewhat tricky, and the documentation doesn’t seem to help much. It seems all the default values for VCS are for probe-based IPMP only.

To achieve link-based IPMP, here’s how I’ve configured my MultiNICB resource:

These are the values you must change from the defaults:

UseMpathd: 1
Tells VCS to use mpathd for network link status
MpathCommand: /usr/lib/inet/in.mpathd -a
The default, /usr/sbin/in.mpathd is just incorrect – it doesn’t live there.
ConfigCheck: 0
If you leave this at 1, it will overwrite your /etc/hostname.xxx files with probe-based IPMP configuration
Device: (your IPMP interfaces here)
The “interface alias” for each device is not needed, leave them blank.
IgnoreStatus: 0
You want VCS to NOT ignore link status, since this is how link-based IPMP works.
GroupName:
Do not use your IPMP group name here, it’s not needed. VCS is not monitoring the group, mpathd is.

Here’s how it looks in main.cf:

MultiNICB csgmultinic (
UseMpathd = 1
MpathdCommand = “/usr/lib/inet/in.mpathd -a”
ConfigCheck = 0
Device = { ce0 = “”, ce4 = “” }
IgnoreLinkStatus = 0
)