BATMAN gateway is not working

I set up a mesh network with BATMAN and I want to access internet.
The topology is:

internet --- node 1(BATMAN gw server) --- node 2 (BATMAN gw client) --- node 3 (BATMAN gw client)

All nodes are with static IP address.
I could ping from node 1.
However, I couldn't ping from node 2.
And I can see that node 2 has a gateway (using the command "batctl gwl")

Using tcpdump, I can see node 1 and node 3 receiving ARP request for which is not expected.
Is there any thing I did do it wrong?