IPv6 Test Addresses
To configure an IPv6 test address, you use the link-local address, because link-local addresses are tied to the physical interface. Thus, you do not need a separate IP address in the IPv6 situation. For IPv6, the -failover option has the following syntax:
# ifconfig interface-name inet6 -failover |
"How to Configure a Multipathing Interface Group With Two Interfaces" shows the steps you perform for an IPv6 test address.
When a multipathing group has both IPv4 and IPv6 plumbed on all the group's interfaces, you might not need a separate IPv4 test address. The in.mpathd daemon can probe the interfaces by using an IPv6 link-local address. IPv6 link-local addresses are created when IPv6 is plumbed.
Use failover without the dash to turn on the failover attribute of the address.
Note - The only valid IPv6 test address is the link-local address.
Preventing Applications From Using Test Addresses
After you have configured a test address, you need to ensure that this address is not used by normal applications. If you let applications use the test address, applications fail, because test addresses do not fail over during the failover operation. To ensure that IP does not pick the test address for normal applications, you mark the test address deprecated by using the ifconfig command. This parameter has the following syntax:
ifconfig interface-name deprecated |
After you mark the address as deprecated, IP does not pick this address as a source address for any communication, unless the applications explicitly bind to the address. Only in.mpathd explicitly binds to such an address. See "How to Configure a Multipathing Interface Group With Two Interfaces".
Because link-local addresses are not present in the name service (DNS, NIS, and NIS+), applications do not use link-local addresses for communication. Consequently, you do not need to mark IPv6 test addresses as deprecated.
Note - You must not mark IPv6 link-local addresses as deprecated.
Use the -deprecated option to turn off the deprecated attribute of the address.
Note - IPv4 test addresses should not be placed in the name service tables (DNS/NIS/NIS+). In IPv6, link-local addresses are used as test addresses and are not normally placed in the name service tables.
Autoconfigured IPv6 addresses are not preserved across system reboot. If you require that IP addresses be preserved across reboot, then applications should use static IP addresses.
Using the hostname File to Configure Groups and Test Addresses
You can use the /etc/hostname.interface files to configure multipathing groups and test addresses. To configure a multipathing group by using the /etc/hostname.interface file, you can add a line to the file by using the following syntax:
interface-address <parameters> group group-name up \ addif logical-interface-address <parameters> up |
For example, to create the group test with the following configuration:
Physical interface hme0 with address 19.16.85.19
A logical interface address of 19.16.85.21
With deprecated and -failover set
Sets the netmask and broadcast address to the default value
You add the following line to the /etc/hostname.hme0 file:
19.16.85.19 netmask + broadcast + group test up \ addif 19.16.85.21 deprecated -failover netmask + broadcast + up |
"How to Configure a Multipathing Interface Group With Two Interfaces" shows the steps you perform to configure the IPv4 hostname file.
For IPv6 setup, add a line to the /etc/hostname6.interface file by using the following syntax:
<parameter> group group-name up |
For example, to create a test group for hme0 with an IPv6 test address, add the following line to the /etc/hostname6.hme0 file:
-failover group test up addif 1080::56:a00:20ff:feb9:19fa up |
"How to Configure a Multipathing Interface Group With Two Interfaces" shows the steps you perform to configure the IPv6 hostname6 file.
Configuring Standby Interfaces
You can configure multipathing groups with standby interfaces. As the name implies, the interface is considered as standby and is not used unless some other interface in the group fails. A standby interface has an IFF_INACTIVE flag when the interface is not hosting any failover IP address. Consequently, when an active interface fails, the standby interface is always chosen for failover. After the standby interface is chosen, the IFF_INACTIVE flag is cleared on the standby interface. From that instant, the active standby is treated the same as other active interfaces. That is, some failures might not choose a standby interface. Instead, some failures might choose an active interface that hosts fewer IP addresses than the standby interface.
The standby interface is not used to send normal data packets. Consequently, limited traffic flows on a standby interface. You must configure standby interfaces with a test address to ensure that probes are sent to determine if the interface is functional. If you do not configure standby interfaces with a test address, the interface is not chosen for failovers when another interface in the group fails. A standby interface might carry traffic under the following conditions:
If another host on the network communicates with a host by using the standby interface address, the standby interface is subsequently used for incoming packets.
Applications binding (either using bind or using IP_ADD_MEMBERSHIP) to the address that is hosted on the standby interface might continue to generate traffic by using the standby interface.
Thus, the system does not normally select a standby interface (except for probes), unless it is explicitly chosen by an application. If some interface in the group fails, all network access is failed over to the standby interface. To configure a standby interface, you use the ifconfig command's new standby parameter by using the following syntax:
# ifconfig interface-name standby group group-name |
"How to Configure a Multipathing Group With One of the Interfaces a Standby Interface" shows the steps you perform.
The in.mpathd daemon sends probes on the standby interface after a test address is configured on the standby interface. You should configure only test addresses on a standby interface. If any other address is added on the standby, the addition of this address fails. If standby is marked on an interface that already has addresses other than test addresses, automatic failover of these addresses occurs to a different interface in the group, leaving behind only the test address, if one exists. It is advisable not to configure non-test address on a standby interface.
You need to mark the address as a test address by using the ifconfig command's deprecated and -failover options before setting standby or setting up.
To configure a test address on a standby interface, use the following syntax:
# ifconfig interface-name plumb ip-address <other-parameters> deprecated -failover standby up |
For <other-parameters>, use the parameters that are required by your configuration. See the ifconfig(1M) man page for descriptions.
Note - Standby interfaces are not used for failover if no test address is configured on that interface.
For example, to create a test address with the following configuration:
Physical interface hme2 as a standby interface
Address of 19.16.85.22
With deprecated and -failover set
Sets the netmask and broadcast address to the default value
You type the following command line:
# ifconfig hme2 plumb 19.16.85.22 netmask + broadcast + deprecated -failover standby up |
Note - The interface is marked as a standby interface only after the address is marked as a NOFAILOVER address.
"How to Configure a Multipathing Group With One of the Interfaces a Standby Interface" shows the steps you perform.
You can clear a standby interface by using the following syntax:
# ifconfig interface-name -standby |
Administering Multipathing Groups With a Single Physical Interface
When you have only one network adapter in the multipathing group, you can configure the network adapter to detect failures on that NIC alone.
Although failovers cannot occur with only one NIC in the group, you still need a separate test address on each of the physical interfaces in the group. You can configure the test address as an IFF_NOFAILOVER address, which is sufficient for the daemon to send out probes on that interface. Unlike the multiple physical interface instance, you do not have to mark a single physical interface as deprecated.
Use the following syntax to configure the interface's IPv4 address as a NOFAILOVER:
# ifconfig interface-name -failover group group-name |
For IPv6, use the following syntax:
# ifconfig interface-name inet6 -failover group group-name |
When the daemon detects failures, the interface is marked and logged appropriately on the console.
Note - You cannot verify whether the target that is being probed has failed or the NIC has failed, because the target can be probed through only one physical interface. If only one default router is on the subnet, turn off multipathing if a single physical interface is in the group. If a separate IPv4 and IPv6 default router exists (or multiple default routers exist), more than one target needs to be probed. Hence, you can safely turn on multipathing.