in.mpathd(1M)                                                                                                                        in.mpathd(1M)

NAME

       in.mpathd - daemon for network adapter (NIC) failure detection, recovery, automatic failover and failback

SYNOPSIS

       /usr/lib/inet/in.mpathd

       The  in.mpathd  daemon performs Network Interface Card (NIC) failure and repair detection. In the event of a NIC failure, it causes IP net-
       work 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  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, 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 meth-
       ods indicates 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 neighboring
       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 sufficient 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 fail-
       ure. 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 configured 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 previously failed NIC, after it has detected a NIC repair. To disable this,
       set the value of FAILBACK to no in /etc/default/mpathd.

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

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

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

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

       Test address address is not unique; disabling probe based failure detection

         In order for in.mpathd to perform probe-based failure detection, each configured test address on the system must  be  unique.  Since  the
         IPv6 test address is a link-local address derived from the ethernet address, each NIC 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_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 is time ms

         The round trip time for ICMP probes is higher than necessary to maintain 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)

         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 interface_name2

         in.mpathd  has  caused the network traffic to failover from NIC interface_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 operational. 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 interface_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 interface_name has been set, indicating the link has come up.

                                                                    4 May 2004                                                       in.mpathd(1M)