Fortigate -- Setup auto initiate the VPN connection by Fortigate Dialup unit

As my posted before, we replaced the firewall on Shanghai office to Fortigate 60B and it used two dynamic PPPoE DSL for internet and VPN connection. Everything works smoothly but we found that the VPN tunnel can't create automatically and needs traffic triggered by dialup side to create the VPN tunnel. The tunnel can't be created by dialup server. It means that if users behind of dialup server and need to access to the resource behind of dialup client but VPN tunnel is not created, the access will fail. It is annoying.
To solve this issue, we need to enable auto-negotiate on Fortigate dialup client side through CLI mode.
Please refer the example configuration as below:
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config vpn ipsec phase2
    edit "VPN_IKE"
        set auto-negotiate enable
        set keepalive enable
        set phase1name "VPN"
        set proposal aes128-sha1
        set dhgrp 1
        set dst-subnet 192.168.11.0 255.255.255.0
        set src-subnet 192.168.22.0 255.255.255.0
    next
end
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After enable the auto-negotiate function on phase2 IKE, the VPN tunnel can create automatically and I don't have to worry about users can't access to remote resource through VPN tunnel.