Seu gateway padrão é a saída de
nmcli d show | grep gw
Exemplo de saída,
IP4.ADDRESS[1]: ip = 192.168.20.61/24, gw = 192.168.20.11 IP6.ADDRESS[1]: ip = 2a02:8108:2380:2ef0:99f4:8f6d:f30e:c089/64, gw = fe80::3681:c4ff:feaf:8198 IP6.ADDRESS[2]: ip = 2a02:8108:2380:2ef0:a00:27ff:fe4f:20ab/64, gw = fe80::3681:c4ff:feaf:8198 IP6.ADDRESS[3]: ip = fe80::a00:27ff:fe4f:20ab/64, gw = fe80::3681:c4ff:feaf:8198 IP4.ADDRESS[1]: ip = 127.0.0.1/8, gw = 0.0.0.0 IP6.ADDRESS[1]: ip = ::1/128, gw = ::
Compare a saída com a saída de
$ ip route | grep default default via 192.168.20.11 dev eth0 proto static metric 100