Unnumbered ipv4 interfaces

[jbemmel]

Test cases like bgp/21-dual-stack-unnumbered configure an unnumbered ipv4 address based on the system loopback.
However, some platforms - like SR Linux - also support simply enabling ipv4 on the interface, without the unnumbered IP

 --{ + running }--[ interface ethernet-1/1 ]--
A:admin@dut# info
    description "dut ~ x1"
    admin-state enable
    subinterface 0 {
        description "dut ~ x1"
        ipv4 {
            admin-state enable
            unnumbered {
                admin-state enable
                interface system0.0
            }
        }

I can delete the 'unnumbered' stanza and the test still passes

Would it make sense to distinguish between these 2 cases, and support enabling ipv4 without assigning an address?

[ipspace]

Would it make sense to distinguish between these 2 cases, and support enabling ipv4 without assigning an address?

Nope. ipv4: True means "this interface can run IPv4, but does not have its own IPv4 address". The implementation is up to the creator of the configuration template.

However, I suspect you might have a problem with anything but EBGP-over-LLA running over that interface. For example, what source IP address will OSPFv2 use? What will be the source IP address in "ICMP TTL exceeded" reply to a traceroute?