Less known Solaris features - IP Multipathing (Appendix A): if_mpadm
Of course it’s a little bit tedious to zip cables from your switch to test IPMP or to deconfigure an interface to force traffic on different interfaces when you want to do some maintainance work in your network. There is an command to on- and offline physical connections in an IPMP group. It’s called
Let’s check, if we have an working IPMP configuration:
Looks good. Now let’s offline one of the interfaces. We will now offline the interface
aggregate0 with the
Okay, now let’s check the IPMP system again:
You will see some important differences. At first
rge0 is now responsible for multicasts and broadcasts. It switched over from
aggregate0. Furthermore you will see, that
aggregate0 is not longer active, the probing is disabled and the state has switched to “offline”.
When you look into the output of
ipmpstat -a, you will recognize that
aggregate0 isn’t used for inbound as well as for outbound traffic of the interface
hivemind-prod. So it worked as designed.
Okay, lets’ play a little bit with this command:
if_mpadm tool prevents you from shooting into your own foot by denying the offlining of the last functional interface in the ipmp group. Now let’s put the device online again.
aggreagte0 interface reappeared as an active device. Now we are able to disable the
Let’s check the status of the IPMP subsystem:
When you look at the
ifconfig -a output you will recognize some additional flags.
When an interface has been offlined, it doesn’t carry the
UP flag, but it got the
OFFLINE flag instead. By the way: As the interface is still perfectly operational (just offlined by the admin) it keeps the
RUNNING flag. Now we reactivate the
Let’s look at the
ifconfig -a output again:
OFFLINE flag disappeared and the
UP status reappeared.
if_mpadm is a somewhat less known and small tool, albeit every admin working with IP Multipathing should know it, as it’s really useful for testing and maintainance purposes.