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<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 ni0: flags=201000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> 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<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> 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<UP,LOOPBACK,RUNNING,MULTICAST,IPv6,VIRTUAL> mtu 8252 index 1 inet6 ::1/128
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<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 ni0: flags=289000842<BROADCAST,RUNNING,MULTICAST,IPv4,NOFAILOVER,OFFLINE,CoS> mtu 0 index 2 inet 0.0.0.0 netmask 0 groupname ipmp0 ether 0:45:e8:33:3c:97 ni1: flags=201000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> 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<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> mtu 1500 index 3 inet 192.168.1.5 netmask ffffff00 broadcast 192.168.1.255 lo0: flags=2002000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv6,VIRTUAL> mtu 8252 index 1 inet6 ::1/128
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<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 ni0: flags=201000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> 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<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> 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<UP,LOOPBACK,RUNNING,MULTICAST,IPv6,VIRTUAL> mtu 8252 index 1 inet6 ::1/128
IPMP is pretty neat, and the next major release has some impressive features (I especially dig ipmpstat)!