in.mpathd(1M)
NAME
in.mpathd - daemon for network adapter (NIC) failure detec-
tion, recovery, 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 opera-
tional NIC that has been configured as part of the same net-
work multipathing group. Once the failed NIC is repaired,
all network access will be restored to the repaired NIC.
in.mpathd needs a special test address on each NIC for the
purpose of sending and receiving probes on each 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 indi-
cated by the IFF_RUNNING flag, allowing for faster failure
detection when the link goes down. The in.mpathd daemon con-
siders a NIC to have failed if either of the above two
methods 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 config-
ured 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 config-
ured, 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_INTERFACES_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 configured as part of a multipathing group. You can
set TRACK_INTERFACES_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. However, in.mpathd cannot
do failover from a failed NIC if it is not part of a mul-
tipathing 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.
FILES
/etc/default/mpathd
Contains default values used by the in.mpathd daemon.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsr |
|_____________________________|_____________________________|
SEE ALSO
ifconfig(1M), attributes(5), icmp(7P), icmp6(7P),
System Administration Guide: IP Services
DIAGNOSTICS
IFF_NOFAILOVER address address is not unique and failure
detection is not possible
Every test address that is configured must be unique on
the system. Otherwise in.mpathd cannot do failure detec-
tion. Since the IPv6 test address is a link-local
address, which in turn is 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.
Failures cannot be detected on interface_name as no
IFF_NOFAILOVER address is available
Every NIC that is configured as part of a multipathing
group must have a test address, which can be either IPv4
or IPv6, or both. Otherwise in.mpathd cannot probe the
NIC, and this message is displayed.
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 the
specified failure detection time. The network is prob-
ably 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)
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.
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