Need help on Android 6.0 on : how to enable the ip forward functionalityvia adb on Android 6.0

[Yang Sean]

In a recent project , I have enabled 2 network cards on the Android 6.0(1 for internal networks and 2 for external internet, the client can ping its own gateway by now )---now I want to enable the ip forward for these 2 networks so that intranet client also can access internet via network 2, but it seems it can't work if I input the following cmd via adb:

  

    echo 1 > /proc/sys/net/ipv4/ip_forward

Is there anyway to prove ip_forward dose work as expected ?