Create a dummy interface

For routes to be installed into the kernel, the source IP must be bound to an interface. Often the CRXN address is not on any interface. Therefore one creates a dummy interface. Alternatively, you can bind the CRXN IP address to the loopback interface. If the CRXN IP address is not bound to an interface, the Netlink: Invalid argument error can occur at bird.

You can create a dummy interface with the following command:

ip link add crxn type dummy
ip link set dev crxn up

Here crxn is the name of the interface.

To bind the CRXN IP address to the interface you can use the following command:

ip addr add dev crxn <ip>/128

Replace <ip> with the CRXN IP address.

To delete the dummy interface you can use the following command:

ip link del crxn

Automatic start with ifupdown

auto crxn
iface crxn inet6 manual
    pre-up ip link add crxn type dummy
    up ip addr add dev crxn <ip>/128
    post-down ip link del crxn

Alternatively, you can use the following configuration:

auto crxn
iface crxn inet6 static
    address <ip>
    netmask 128
    pre-up ip link add crxn type dummy
    post-down ip link del crxn

Here the assignment of the IP address is delegated to ifupdown.