Configuring Test Addresses

You must configure all physical interfaces of a multipathing group with a test address. You need test addresses to detect failures and repairs. If a test address is not configured, it is not chosen for failover. Only in.mpathd uses test addresses. Normal applications should not use this address. This address will not failover when the interface fails. In IPv4, you should configure the test address in such a way that normal applications do not use the test address (See How to Configure a Multipathing Interface Group with Two Interfaces).

This section describes test address configuration concepts for the following Internet protocols:

• IPv4

• IPv6

IPv4 Test Addresses

The in.mpathd multipathing daemon requires a test IP address for detecting failures and repairs. You must use a routeable address for this IP address. That is, the subnet prefix of the address must be known to any routers present on the link. You use the ifconfig command's new -failover option to configure a test address. Use the following syntax to configure a test address:

# ifconfig interface-name addif ip-address <other-parameters> -failover up

For <other-parameters>, use the parameters required by your configuration. See the ifconfig(1M) man page for descriptions. How to Configure a Multipathing Interface Group with Two Interfaces shows the steps you perform for an IPv4 test address.

For example, to add a new logical interface with an address of 19.16.85.21, the netmask and broadcast address set to the default value, and also configure the interface with a test address, type the following:

# ifconfig hme0 addif 19.16.85.21 netmask + broadcast + -failover up

You must mark an IPv4 test address as deprecated to prevent applications from using the test address (see How to Configure a Multipathing Interface Group with Two Interfaces).

Use failover without the dash to turn on the failover attribute of the address.

All test IP addresses in a multipathing group must use the same network prefix. That is, the test IP addresses must belong to a single IP subnet.

IPv6 Test Addresses

To configure an IPv6 test address, you use the link-local address itself, because link-local addresses are tied to the physical interface. Thus, you do not need a separate IP address in the IPv6 case. 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 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.

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 will fail, because test addresses do not failover 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.

You must not mark IPv6 link-local addresses as deprecated.

Use the -deprecated option to turn off the deprecated attribute of the address.

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.