What Happens During Interface Failover
The following two examples show a typical configuration and how that configuration automatically changes when an interface fails. When the hme0 interface fails, notice that all data addresses move from hme0 to hme1.
Example 30–1 Interface Configuration Before an Interface Failure
hme0: flags=9000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4>
mtu 1500 index 2
inet 192.168.85.19 netmask ffffff00 broadcast 192.168.85.255
groupname test
hme0:1: flags=9000843<UP,BROADCAST,RUNNING,MULTICAST,DEPRECATED,IPv4,NOFAILOVER>
mtu 1500
index 2 inet 192.168.85.21 netmask ffffff00 broadcast 192.168.85.255
hme1: flags=9000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2
8 inet 192.168.85.20 netmask ffffff00 broadcast 192.168.85.255
groupname test
hme1:1: flags=9000843<UP,BROADCAST,RUNNING,MULTICAST,DEPRECATED,IPv4,NOFAILOVER>
mtu 1500
index 2 inet 192.168.85.22 netmask ffffff00 broadcast 192.168.85.255
hme0: flags=a000841<UP,RUNNING,MULTICAST,IPv6,NOFAILOVER> mtu 1500 index 2
inet6 fe80::a00:20ff:feb9:19fa/10
groupname test
hme1: flags=a000841<UP,RUNNING,MULTICAST,IPv6,NOFAILOVER> mtu 1500 index 2
inet6 fe80::a00:20ff:feb9:1bfc/10
groupname test
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Example 30–2 Interface Configuration After an Interface Failure
hme0: flags=19000842<BROADCAST,RUNNING,MULTICAST,IPv4,
NOFAILOVER,FAILED> mtu 0 index 2
inet 0.0.0.0 netmask 0
groupname test
hme0:1: flags=19040843<UP,BROADCAST,RUNNING,MULTICAST,DEPRECATED,IPv4,
NOFAILOVER,FAILED> mtu 1500 index 2
inet 192.168.85.21 netmask ffffff00 broadcast 10.0.0.255
hme1: flags=9000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2
inet 192.168.85.20 netmask ffffff00 broadcast 192.168.85.255
groupname test
hme1:1: flags=9000843<UP,BROADCAST,RUNNING,MULTICAST,DEPRECATED,IPv4,
NOFAILOVER> mtu 1500
index 2 inet 192.168.85.22 netmask ffffff00 broadcast 10.0.0.255
hme1:2: flags=1000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 6
inet 192.168.85.19 netmask ffffff00 broadcast 192.168.18.255
hme0: flags=a000841<UP,RUNNING,MULTICAST,IPv6,NOFAILOVER,FAILED> mtu 1500 index 2
inet6 fe80::a00:20ff:feb9:19fa/10
groupname test
hme1: flags=a000841<UP,RUNNING,MULTICAST,IPv6,NOFAILOVER> mtu 1500 index 2
inet6 fe80::a00:20ff:feb9:1bfc/10
groupname test
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You can see that the FAILED flag is set on hme0 to indicate that this interface has failed. You can also see that hme1:2 has been created. hme1:2 was originally hme0. The address 192.168.85.19 then becomes accessible through hme1.
Multicast memberships that are associated with 192.168.85.19 can still receive packets, but they now receive packets through hme1. When the failover of address 192.168.85.19 from hme0 to hme1 occurred, a dummy address 0.0.0.0 was created on hme0. The dummy address was created so that hme0 can still be accessed. hme0:1 cannot exist without hme0. The dummy address is removed when a subsequent failback takes place.
Similarly, failover of the IPv6 address from hme0 to hme1 occurred. In IPv6, multicast memberships are associated with interface indexes. Multicast memberships also fail over from hme0 to hme1. All the addresses that in.ndpd configured also moved. This action is not shown in the examples.
The in.mpathd daemon continues to probe through the failed interface hme0. After the daemon receives 10 consecutive replies for a default repair detection time of 20 seconds, the daemon determines that the interface is repaired. Because the RUNNING flag is also set on hme0, the daemon invokes the failback. After failback, the original configuration is restored.
For a description of all error messages that are logged on the console during failures and repairs, see the in.mpathd(1M) man page.
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