Ты меняешь mac адрес но IP остается тот же, поэтому сервер dhcp отвечает некорректно.
Попробуй так:
ifconfig eth0 down
ifconfig eth0 0.0.0.0
macchanger -r eth0
ifconfig eth0 up
dhclient eth0
не проканало
root@kali:~# ifconfig eth0 down
root@kali:~# ifconfig eth0 0.0.0.0
root@kali:~# macchanger -r eth0
Current MAC: 62:e4:74:9b:6d:97 (unknown)
Permanent MAC: 08:00:27:18:59:0b (CADMUS COMPUTER SYSTEMS)
New MAC: 32:d0:a6:7f:7b:ae (unknown)
root@kali:~# ifconfig eth0 up
root@kali:~# dhclient eth0
root@kali:~# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
From 192.168.1.31 icmp_seq=1 Destination Host Unreachable
From 192.168.1.31 icmp_seq=2 Destination Host Unreachable
From 192.168.1.31 icmp_seq=3 Destination Host Unreachable
From 192.168.1.31 icmp_seq=4 Destination Host Unreachable
From 192.168.1.31 icmp_seq=5 Destination Host Unreachable
From 192.168.1.31 icmp_seq=6 Destination Host Unreachable
^C
--- 8.8.8.8 ping statistics ---
7 packets transmitted, 0 received, +6 errors, 100% packet loss, time 6121ms
pipe 4