[HD2 Android NAND Development] LiFE1688:
tyween,

Before turning on WiFi

[mobiledata.interfaces]: [rmnet0,rmnet1,rmnet2]
[ro.telephony.default_network]: [0]
[net.bt.name]: [Android]
[net.change]: [net.dnschange]
[COLOR="Red"][net.ppp0.dns1]: [8.8.8.8]
[net.ppp0.dns2]: [8.8.4.4]
[net.dns1]: [208.67.220.220]
[net.dns2]: [208.67.222.222]
[net.dns3]: [8.8.8.8][/COLOR]
[net.tcp.buffersize.default]: [4096,87380,110208,4096,16384,110208]
[net.tcp.buffersize.wifi]: [4095,87380,110208,4096,16384,110208]
[net.tcp.buffersize.umts]: [4094,87380,110208,4096,16384,110208]
[net.tcp.buffersize.edge]: [4093,26280,35040,4096,16384,35040]
[net.tcp.buffersize.gprs]: [4092,8760,11680,4096,8760,11680]
[init.svc.netd]: [running]
[net.hostname]: [android-1201fb84a8a805c]
[net.gprs.http-proxy]: []
[gsm.network.type]: [UMTS]
[net.dnschange]: [1]

After turning on WiFi

[mobiledata.interfaces]: [rmnet0,rmnet1,rmnet2]
[ro.telephony.default_network]: [0]
[net.bt.name]: [Android]
[net.change]: [net.dnschange]
[COLOR="Red"][net.ppp0.dns1]: []
[net.ppp0.dns2]: []
[net.dns1]: [192.168.0.1]
[net.dns2]: [208.67.222.222]
[net.dns3]: [8.8.8.8][/COLOR]
[net.tcp.buffersize.default]: [4096,87380,110208,4096,16384,110208]
[net.tcp.buffersize.wifi]: [4095,87380,110208,4096,16384,110208]
[net.tcp.buffersize.umts]: [4094,87380,110208,4096,16384,110208]
[net.tcp.buffersize.edge]: [4093,26280,35040,4096,16384,35040]
[net.tcp.buffersize.gprs]: [4092,8760,11680,4096,8760,11680]
[init.svc.netd]: [running]
[net.hostname]: [android-1201fb84a8a805c]
[net.gprs.http-proxy]: []
[gsm.network.type]: [UMTS]
[net.dnschange]: [6]

After turning off WiFi

getprop | grep net
[mobiledata.interfaces]: [rmnet0,rmnet1,rmnet2]
[ro.telephony.default_network]: [0]
[net.bt.name]: [Android]
[net.change]: [net.dnschange]
[COLOR="Red"][net.ppp0.dns1]: [165.21.83.88]
[net.ppp0.dns2]: [165.21.100.88]
[net.dns1]: []
[net.dns2]: [208.67.222.222]
[net.dns3]: [8.8.8.8]
[/COLOR][net.tcp.buffersize.default]: [4096,87380,110208,4096,16384,110208]
[net.tcp.buffersize.wifi]: [4095,87380,110208,4096,16384,110208]
[net.tcp.buffersize.umts]: [4094,87380,110208,4096,16384,110208]
[net.tcp.buffersize.edge]: [4093,26280,35040,4096,16384,35040]
[net.tcp.buffersize.gprs]: [4092,8760,11680,4096,8760,11680]
[init.svc.netd]: [running]
[net.hostname]: [android-1201fb84a8a805c]
[net.gprs.http-proxy]: []
[gsm.network.type]: [UMTS]
[net.dnschange]: [8]

Notice [net.dns1] is missing?

Present "ip-up"

#!/system/bin/sh
#author: cedesmith

PATH=/sbin:/system/sbin:/system/bin:/system/xbin

setprop net.ppp0.dns1 $DNS1
setprop net.ppp0.dns2 $DNS2

The reason why deleting ip-up works is because after a reboot, the DNS is set via "build.prop"

net.ppp0.dns1=208.67.220.220
net.ppp0.dns2=208.67.222.222
net.dns1=208.67.220.220
net.dns2=208.67.222.222
net.dns3=8.8.8.8

which is why the first getprop | grep net shows the correct DNS.

However after a wifi connection, your ip-up causes the net.ppp0.dns1, net.ppp0.dns2 and net.dns1 to change.

Your setprop took care of net.ppp0.dns1 and net.ppp0.dns2 but did not replace net.dns1.

For me, I prefer ip-up to be

#!/system/bin/sh
#author: cedesmith

PATH=/sbin:/system/sbin:/system/bin:/system/xbin

setprop net.ppp0.dns1 208.67.220.220
setprop net.ppp0.dns2 208.67.222.222
setprop net.dns1 208.67.220.220
setprop net.dns2 208.67.222.222
setprop net.dns3 8.8.8.8

This way, the DNS is always the same as when you first rebooted, exactly the same as the build.prop. The only problem I can foresee is when someone tries to get on wifi, and the network admin forces people to use specific DNS instead your own.

The other stupid thing is although you have net.dns1 net.dns2 and net.dns3, it only uses the value of net.dns1 when it is empty, totally ignoring the 2nd and 3rd.