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Hierarchy Level


For unnumbered Ethernet interfaces configured with a loopback interface as the donor interface, specify one of the loopback interface’s secondary addresses as the preferred source address for the unnumbered Ethernet interface. Configuring the preferred source address enables you to use an IP address other than the primary IP address on some of the unnumbered Ethernet interfaces in your network. To configure the preferred source address dynamically, instead of using this statement, you must include the $junos-preferred-source-address predefined variable for IPv4 (family inet) addresses or the $junos-preferred-source-ipv6-address predefined variable for IPv6 (family inet6) addresses.

Configuration of a preferred source address for unnumbered Ethernet interfaces is supported for IPv4 and IPv6 address families.


When you specify a static logical interface for the unnumbered interface in a dynamic profile that includes the $junos-routing-instance predefined variable, you must not configure a preferred source address, whether with the $junos-preferred-source-address predefined variable, the $junos-preferred-source-ipv6-address predefined variable, or the preferred-source-address statement. Configuring the preferred source address in this circumstance causes a commit failure.


address—Secondary IP address of the donor loopback interface. Alternatively, use the $junos-preferred-source-address or the $junos-preferred-source-ipv6-address predefined variable to dynamically apply a preferred source address to the unnumbered Ethernet interface.

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 9.2.

Support for the $junos-preferred-source-address and $junos-preferred-source-ipv6-address predefined variables introduced in Junos OS Release 9.6.