Taking IPMP managed interfaces online and offline


I use Solaris IPMP (IP multipathing) on several of my servers to allow them to keep operating in the event that a network interface or switch were to fail. Periodically I need to take IPMP managed interfaces offline, but I need to keep the IP addresses attached to those interface up and operational. Solaris comes with the if_mpadm utility, which provides a simple and straight forward way to take IPMP managed interfaces online and offline.

Prior to using the if_mpadm utility, it is useful to check the status of the interface you want to take online or offline. This can be done by running the ifconfig utility, and checking the status of the interface you are interested in taking online or offline (in this case ni0):

$ ifconfig -a

lo0: flags=2001000849 mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 ni0: flags=201000843 mtu 1500 index 2 inet 192.168.1.5 netmask ffffff00 broadcast 192.168.1.255 groupname ipmp0 ether 0:45:e8:33:3c:97 ni1: flags=201000843 mtu 1500 index 3 inet 0.0.0.0 netmask ff000000 broadcast 0.255.255.255 groupname ipmp0 ether 0:72:b6:d3:ee:35 lo0: flags=2002000849 mtu 8252 index 1 inet6 ::1128

To take the interface ni0 offline for maintenance, the if_mpadm utility can be run with the “-d” option (take interface offline), and the name of the interface to take offline:

$ if_mpadm -d ni0

Once if_mpadm does it’s job, the interface will be in the OFFLINE state, and the IP addresses attached to that interface will have migrated to another device in the IPMP group:

$ ifconfig -a

lo0: flags=2001000849 mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 ni0: flags=289000842 mtu 0 index 2 inet 0.0.0.0 netmask 0 groupname ipmp0 ether 0:45:e8:33:3c:97 ni1: flags=201000843 mtu 1500 index 3 inet 0.0.0.0 netmask ff000000 broadcast 0.255.255.255 groupname ipmp0 ether 0:72:b6:d3:ee:35 ni1:1: flags=201000843 mtu 1500 index 3 inet 192.168.1.5 netmask ffffff00 broadcast 192.168.1.255 lo0: flags=2002000849 mtu 8252 index 1 inet6 ::1128

After you finish your maintenance, you can use the if_mpadm “-r” option (bring interface online) to bring the interface online:

$ if_mpadm -r ni0

Once if_mpadm completes, you can use the ifconfig utility to verify the interface is back up, and the IP addresses have migrated back to the original adaptor (you can disable automatic failback by setting FAILBACK to no in /etc/default/mpathd):

$ ifconfig -a

lo0: flags=2001000849 mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 ni0: flags=201000843 mtu 1500 index 2 inet 192.168.1.5 netmask ffffff00 broadcast 192.168.1.255 groupname ipmp0 ether 0:45:e8:33:3c:97 ni1: flags=201000843 mtu 1500 index 3 inet 0.0.0.0 netmask ff000000 broadcast 0.255.255.255 groupname ipmp0 ether 0:72:b6:d3:ee:35 lo0: flags=2002000849 mtu 8252 index 1 inet6 ::1128

IPMP is pretty neat, and the next major release has some impressive features (I especially dig ipmpstat)!

This article was posted by Matty on 2007-05-05 09:27:00 -0400 EDT