in.mpathd(1M)						  System Administration Commands					     in.mpathd(1M)

NAME

       in.mpathd - IP multipathing daemon

SYNOPSIS

       /usr/lib/inet/in.mpathd

DESCRIPTION

       The  in.mpathd  daemon performs failure and repair detection for IP interfaces that have been placed into an IPMP group (or optionally, for
       all IP interfaces on the system). It also controls which IP interfaces in an IPMP group are "active" (being used by the system to  send	or
       receive IP data traffic) in a manner that is consistent with the administrator's configured policy.

       The  in.mpathd daemon can detect IP interface failure and repair through two methods: by monitoring the IFF_RUNNING flag for each IP inter-
       face (link-based failure detection), and by sending and receiving ICMP probes on each IP interface (probe-based failure	detection).  Link-
       based  failure  detection  is  instantaneous  and is always enabled (provided the network driver supports the feature); probe-based failure
       detection must be enabled through the configuration of  one or more test addresses (described below), but tests	the  entire  IP  interface
       send and receive path. The ipmpstat(1M) utility can be used to check which failure detection methods are enabled.

       If  only  link-based  failure detection is enabled, then the health of the interface is determined solely from the state of the IFF_RUNNING
       flag. Otherwise, the interface is considered failed if either of the two methods indicate a failure, and repaired once both  methods  indi-
       cate the failure has been corrected. Not all interfaces in a group need to be configured with the same failure detection methods.

       As  mentioned  above,  to  perform  probe-based failure detection in.mpathd requires a test address on each IP interface for the purpose of
       sending and receiving probes. Each address must be marked NOFAILOVER (see ifconfig(1M)) and in.mpathd will be limited to probing targets on
       the  same  subnet.  Each  address  may be configured statically or acquired by means of DHCP. To find targets, in.mpathd first consults the
       routing table for routes on the same subnet, and uses the specified next-hop. If no routes  match,  it  sends  all-hosts  ICMP  probes  and
       selects	a  subset  of the systems that respond. Thus, for probe-based failure detection to operate, there must be at least one neighbor on
       each subnet that responds to ICMP echo request probes. The ipmpstat(1M) utility can be used to display both the current probe target infor-
       mation and the status of sent probes.

       Both  IPv4  and IPv6 are supported. If an IP interface is plumbed for IPv4 and an IPv4 test address is configured then in.mpathd will start
       sending ICMPv4 probes over that IP interface. Similarly, if an IP interface is plumbed for IPv6 and an IPv6  test  address  is  configured,
       then  in.mpathd	will start sending ICMPv6 probes over that IP interface. However, note that in.mpathd will ignore IPv6 test addresses that
       are not link-local. If both IPv4 and IPv6 are plumbed, it is sufficient to configure only one of the two, that  is,  either  an	IPv4  test
       address or an IPv6 test address. If both IPv4 and IPv6 test addresses are configured, in.mpathd probes using both ICMPv4 and ICMPv6.

       As  mentioned  above,  in.mpathd also controls which IP interfaces in an IPMP group are "active" (used by the system to send and receive IP
       data traffic). Specifically, in.mpathd tracks the administrative configuration of each IPMP group and attempts to keep the number of active
       IP  interfaces  in  each  group	consistent with that configuration. Therefore, if an active IP interface fails, in.mpathd will activate an
       INACTIVE interface in the group, provided one exists (it will prefer INACTIVE interfaces that are also marked STANDBY). Likewise, if an	IP
       interface  repairs  and the resulting repair leaves the IPMP group with more active interfaces than the administrative configuration speci-
       fies, in.mpathd will deactivate one of the interfaces (preferably one marked STANDBY), except  when  the  FAILBACK  variable  is  used,	as
       described below. Similar adjustments will be made by in.mpathd when offlining IP interfaces (for instance, in response to if_mpadm(1M)).

       The   in.mpathd	 daemon  accesses  three  variable  values  in	/etc/default/mpathd:  FAILURE_DETECTION_TIME,  FAILBACK  and  TRACK_INTER-
       FACES_ONLY_WITH_GROUPS.

       The FAILURE_DETECTION_TIME variable specifies the probe-based failure detection time. The shorter the  failure  detection  time,  the  more
       probe  traffic.	The  default  value  of  FAILURE_DETECTION_TIME  is  10  seconds. This means that IP interface failure will be detected by
       in.mpathd within 10 seconds. The IP interface repair detection time is always twice the value of FAILURE_DETECTION_TIME. Note that failures
       and  repairs  detected  by link-based failure detection are acted on immediately, though in.mpathd may ignore link state changes if it sus-
       pects that the link state is flapping due to defective hardware; see DIAGNOSTICS.

       By default, in.mpathd limits failure and repair detection to IP interfaces that are configured as part  of  a  named  IPMP  group.  Setting
       TRACK_INTERFACES_ONLY_WITH_GROUPS  to  no  enables  failure and repair detection on all IP interfaces, even if they are not part of a named
       IPMP group. IP interfaces that are tracked but not part of a named IPMP group are considered to be part of the "anonymous" IPMP	group.	In
       addition  to  having  no  name,	this  IPMP group is special in that its IP interfaces are not equivalent and thus cannot take over for one
       another in the event of an IP interface failure. That is, the anonymous IPMP group can only be used for failure and repair  detection,  and
       provides no high-availability or load-spreading.

       As  described  above,  when  in.mpathd detects that an IP interface has repaired, it activates it so that it will again be used to send and
       receive IP data traffic. However, if FAILBACK is set to no, then the IP interface will only be activated if no other active  IP	interfaces
       in the group remain. However, the  interface may subsequently be activated if another IP interface in the group fails.

FILES

       /etc/default/mpathd    Contains default values used by the in.mpathd daemon.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsr			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       if_mpadm(1M), ifconfig(1M), ipmpstat(1M), attributes(5), icmp(7P), icmp6(7P),

       System Administration Guide: IP Services

DIAGNOSTICS

       IP interface  interface_name has a hardware  address which is not unique in group group_name; offlining
	   Description:

	   For	probe-based  failure  detection, load-spreading, and other code IPMP features to work properly, each IP interface in an IPMP group
	   must have a unique hardware address. If this requirement is not met, in.mpathd will automatically offline all but one of the IP  inter-
	   faces with duplicate hardware addresses.

       IP interface interface_name now has a unique hardware address in group group_name; onlining
	   Description:

	   The previously-detected duplicate hardware address is now unique, and therefore in.mpathd has brought interface_name back online.

       Test address address is not unique in group; disabling probe-based failure detection on interface_name
	   Description:

	   For in.mpathd to perform probe-based failure detection, each test address in the group must be unique.

       No test address configured on interface interface_name disabling probe-based failure detection on it
	   Description:

	   For	in.mpathd  to  perform probe-based failure detection on an IP interface, it must be configured with a test address: IPv4, IPv6, or
	   both.

       IP interface_name in group group_name is not plumbed for IPv[4|6], affecting IPv[4|6] connectivity
	   Description:

	   All IP interfaces in a multipathing group must be homogeneously plumbed. For example, if one IP interface is plumbed for IPv4, then all
	   IP  interfaces  in  the  group must be plumbed for IPv4, or IPv4 packets will not be able to be reliably sent and received. The STREAMS
	   modules pushed on all IP interfaces must also be identical.

       The link has come up on interface_name more than 2 times in the last minute; disabling repair until it stabilizes.
	   Description:

	   To limit the impact of interfaces with intermittent hardware (such as a bad cable), in.mpathd will not consider an IP interface with  a
	   frequently changing link state as repaired until the link state stabilizes.

       Invalid failure detection time of time, assuming default 10000 ms
	   Description:

	   An invalid value was encountered for FAILURE_DETECTION_TIME in the /etc/default/mpathd file.

       Too small failure detection time of time, assuming minimum of 100 ms
	   Description:

	   The minimum value that can be specified for FAILURE_DETECTION_TIME is currently 100 milliseconds.

       Invalid value for FAILBACK value
	   Description:

	   Valid values for the boolean variable FAILBACK are yes or no.

       Invalid value for TRACK_INTERFACES_ONLY_WITH_GROUPS value
	   Description:

	   Valid values for the boolean variable TRACK_INTERFACES_ONLY_WITH_GROUPS are yes or no.

       Cannot meet requested failure detection time of time ms on (inet[6] interface_name) new failure detection time for group group_name is time
       ms
	   Description:

	   The round trip time for ICMP probes is higher than necessary to maintain the current failure detection time. The  network  is  probably
	   congested  or  the  probe  targets  are loaded. in.mpathd automatically increases the failure detection time to whatever it can achieve
	   under these conditions.

       Improved failure detection time time ms on (inet[6] interface_name) for group group_name
	   Description:

	   The round trip time for ICMP probes has now decreased and in.mpathd has lowered the failure detection time correspondingly.

       IP interface failure detected on interface_name
	   Description:

	   in.mpathd has detected a failure on interface_name, and has set the IFF_FAILED flag on interface_name, ensuring that  it  will  not	be
	   used for IP data traffic.

       IP interface repair detected on interface_name
	   Description:

	   in.mpathd  has detected a repair on interface_name, and has cleared the IFF_FAILED flag. Depending on the administrative configuration,
	   the interface_name may again be used for IP data traffic.

       The link has gone down on interface_name
	   Description:

	   in.mpathd has detected that the IFF_RUNNING flag for interface_name has been cleared, indicating that the link has gone down.

       The link has come up on interface_name
	   Description:

	   in.mpathd has detected that the IFF_RUNNING flag for interface_name has been set, indicating that the link has come up.

SunOS 5.11							    20 Jan 2009 						     in.mpathd(1M)