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

NAME
       in.mpathd  - daemon for network adapter (NIC) failure detection, recov‐
       ery, automatic failover and failback

SYNOPSIS
       /usr/lib/inet/in.mpathd

DESCRIPTION
       The in.mpathd daemon performs Network Interface Card (NIC) failure  and
       repair  detection.  In the event of a NIC failure, it causes IP network
       access from the failed NIC to failover to a standby NIC, if  available,
       or  to  any another operational NIC that has been configured as part of
       the same network multipathing group. Once the failed NIC	 is  repaired,
       all network access is restored to the repaired NIC.

       The  in.mpathd  daemon  can  detect  NIC failure and repair through two
       methods: by monitoring the IFF_RUNNING flag for	each  NIC  (link-based
       failure detection), and by sending and receiving ICMP echo requests and
       replies on each NIC (probe-based failure detection). Link-based failure
       detection requires no explicit configuration and thus is always enabled
       (provided the NIC driver supports  the  feature);  probe-based  failure
       detection must be enabled through the configuration of one or more test
       addresses (described below), but has the benefit of testing the	entire
       NIC send and receive path.

       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 indicate the
       failure	has  been  corrected. Not all interfaces in a group need to be
       configured with the same failure detection methods.

       As mentioned above, in order to perform probe-based  failure  detection
       in.mpathd  needs	 a special test address on each NIC for the purpose of
       sending and receiving probes on	the  NIC.  Use	the  ifconfig  command
       -failover  option  to configure these test addresses. See ifconfig(1M).
       The test address must belong to a subnet that is known to the hosts and
       routers on the link.

       The  in.mpathd daemon can detect NIC failure and repair by two methods,
       by sending and receiving ICMP echo requests and replies	on  each  NIC,
       and  by monitoring the IFF_RUNNING flag for each NIC. The link state on
       some models of NIC is indicated by the IFF_RUNNING flag,	 allowing  for
       faster  failure detection when the link goes down. The in.mpathd daemon
       considers a NIC to have failed if either of the above two methods indi‐
       cates  failure. A NIC is considered to be repaired only if both methods
       indicate the NIC is repaired.

       The in.mpathd daemon sends the ICMP  echo  request  probes  to  on-link
       routers.	 If no routers are available, it sends the probes to neighbor‐
       ing hosts. Thus, for network failure detection and repair,  there  must
       be  at  least  one  neighbor  on	 each  link that responds to ICMP echo
       request probes.

       in.mpathd works on both IPv4 and IPv6. If IPv4 is plumbed on a NIC,  an
       IPv4 test address is configured on theNIC, and the NIC is configured as
       part of a network multipathing group, then in.mpathd will start sending
       ICMP probes on the NIC using IPv4.

       In  the	case of IPv6, the link-local address must be configured as the
       test address. The in.mpathd daemon will	not  accept  a	non-link-local
       address	as a test address. If the NIC is part of a multipathing group,
       and the test address has been configured, then in.mpathd will probe the
       NIC for failures using IPv6.

       Even if both the IPv4 and IPv6 protocol streams are plumbed, it is suf‐
       ficient to configure only one of the two, that is, either an IPv4  test
       address	or an IPv6 test address on a NIC. If only an IPv4 test address
       is configured, it probes using  only  ICMPv4.  If  only	an  IPv6  test
       address	is  configured, it probes using only ICMPv6. If both type test
       addresses are configured, it probes using both ICMPv4 and ICMPv6.

       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 NIC failure detection
       time  for  the ICMP echo request probe method of detecting NIC failure.
       The shorter the failure detection time, the greater the volume of probe
       traffic.	 The  default  value  of FAILURE_DETECTION_TIME is 10 seconds.
       This means that NIC failure will be detected  by	 in.mpathd  within  10
       seconds.	 NIC  failures	detected by the IFF_RUNNING flag being cleared
       are acted on as soon as the in.mpathd daemon notices the change in  the
       flag.  The  NIC repair detection time cannot be configured; however, it
       is defined as double the value of FAILURE_DETECTION_TIME.

       By default, in.mpathd does failure detection only on NICs that are con‐
       figured	as  part  of  a	 multipathing  group. You can set TRACK_INTER‐
       FACES_ONLY_WITH_GROUPS to no to enable failure detection	 by  in.mpathd
       on  all	NICs,  even if they are not part of a multipathing group. How‐
       ever, in.mpathd cannot do failover from a failed NIC if it is not  part
       of a multipathing group.

       The  in.mpathd  daemon  will restore network traffic back to the previ‐
       ously failed NIC, after it has detected a NIC repair. To disable	 this,
       set the value of FAILBACK to no in /etc/default/mpathd.

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

       System Administration Guide: IP Services

DIAGNOSTICS
       Test address address is	not  unique;  disabling	 probe	based  failure
       detection on interface_name

	 For  in.mpathd	 to  perform  probe-based failure detection, each test
	 address in the group must be unique. Since the IPv6 test address is a
	 link-local address derived from the MAC address, each IP interface in
	 the group must have a unique MAC address.

       NIC interface_name of group group_name is not plumbed for IPv[4|6]  and
       may affect failover capability

	 All  NICs  in a multipathing group must be homogeneously plumbed. For
	 example, if a NIC is plumbed for IPv4, then all  NICs	in  the	 group
	 must be plumbed for IPv4. The streams modules pushed on all NICs must
	 be identical.

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

	 In  order for in.mpathd to perform probe-based failure detection on a
	 NIC, it must be configured with a test address: IPv4, IPv6, or both.

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

	 In  order to prevent interfaces with intermittent hardware, such as a
	 bad cable, from causing repeated failovers and	 failbacks,  in.mpathd
	 does  not  failback  to  interfaces  with frequently fluctuating link
	 states.

       Invalid failure detection time assuming default 10000

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

       Too small failure detection time of time assuming minimum 100

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

       Invalid value for FAILBACK value

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

       Invalid value for TRACK_INTERFACES_ONLY_WITH_GROUPS value

	 Valid	  values    for	   the	  boolean    variable	  TRACK_INTER‐
	 FACES_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

	 The round trip time for ICMP probes is higher than necessary to main‐
	 tain the current failure detection time. The network is probably con‐
	 gested	 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

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

       NIC failure detected on interface_name

	 in.mpathd has detected NIC failure on interface_name, and has set the
	 IFF_FAILED flag on NIC interface_name.

       Successfully  failed  over  from	 NIC  interface_name1  to  NIC	inter‐
       face_name2

	 in.mpathd  has caused the network traffic to failover from NIC inter‐
	 face_name1 to NIC interface_name2, which is part of the  multipathing
	 group.

       NIC repair detected on interface_name

	 in.mpathd has detected that NIC interface_name is repaired and opera‐
	 tional. If the IFF_FAILED flag on the NIC was previously set, it will
	 be reset.

       Successfully failed back to NIC interface_name

	 in.mpathd  has	 restored  network traffic back to NIC interface_name,
	 which is now repaired and operational.

       The link has gone down on interface_name

	 in.mpathd has detected that  the  IFF_RUNNING	flag  for  NIC	inter‐
	 face_name has been cleared, indicating the link has gone down.

       The link has come up on interface_name

	 in.mpathd  has	 detected  that	 the  IFF_RUNNING  flag for NIC inter‐
	 face_name has been set, indicating the link has come up.

SunOS 5.10			  8 Sep 2006			 in.mpathd(1M)
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