What does "ip4 default" mean in NetworkManager nmcli output?

Question

My output of nmcli on my machine is as follows:

enp129s0f0: connected to enp129s0f0
        "Intel 82599ES SFI/SFP+"
        ethernet (ixgbe), 00:AB:50:C6:C4:D0, hw, mtu 1500
        ip4 default
        inet4 192.168.99.105/24
        route4 0.0.0.0/0
        route4 192.168.99.0/24

enp5s0f0: connected to enp5s0f0
        "Intel I350"
        ethernet (igb), 00:AB:50:C4:4C:1E, hw, mtu 1500
        inet4 192.168.11.14/24
        route4 192.168.11.0/24
        route4 0.0.0.0/0

What does the ip4 default portion of it mean? Why does it only exist on one interface?

Answer 1

ipv4 default means that this connection is elected to be the default IPv4 gateway for outgoing connections.

If you execute from this commands from the console, you should get output similar to the following:

# ip route | grep 'default via '
default via 192.168.99.0 dev enp129s0f0 proto static metric 105

# ip -o route get to 8.8.8.8
8.8.8.8 via 192.168.99.254 dev enp129s0f0 src 192.168.99.105 uid 0 \    cache

The default is chosen (AFAIK) from all the connection configured with option ipv4.never-default: yes. Never-default is set to no, by default.

This is independent from the method that you use for IP assignment (e.g. static vs DHCP).

Answer 2

This means you have chosen to have NetworkManager configure IPv4 on the connection automatically, rather than manually. For IPv4 it will use DHCP, and for IPv6 it will follow whatever is in the router advertisements.