same result using setprop
# setprop net.dns1 8.8.8.8
# getprop | grep dns
[net.change]: [net.dns1]
[net.dns1]: [8.8.8.8]
# ping google.com
ping: unknown host google.com
# ping 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=110 time=95.8 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=110 time=34.5 ms
^C
--- 8.8.8.8 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 34.513/65.193/95.873/30.680 ms