I have setup my QnX target as WiFi AP. The setup is as follows.

en0 - 192.168.1.102 (dhcp.client) connected to backbone.
wl0 - 192.168.20.1 (dhcpd)

Other WiFi clients are able to associate with WiFi AP and getting IP addresses from dhcpd running in my taget. For 
example: 192.168.20.254 or 192.168.20.253

I have issued following commands for NAT:

sysctl -w net.inet.ip.forwarding=1
mount -Ttcpip lsm-pf-v4.so
pfctl -e -f /etc/pf.conf

From WiFi client, i am able to ping the host (192.168.1.101) that is connected on the backbone and i am able to browse 
the internet. But i am not able to ping 192.168.20.X (neither 192.168.20.1 nor 192.168.20.254) region from the wired 
host (192.168.1.102).

My /etc/pf.conf is as follows

"nat on en0 from wl0/24 to any -> en0"

Please let me know how to make the ping from External network (192.168.1.X) to internal network (192.168.20.X) to work.

Thanks & Regards,
Nizam.

     ----------------------------------------
      Ethernet Client (192.168.1.101)
     -----------------------------------------
                  |
                  |
      ---------------------------------------
       Router (192.168.1.1) --------------------------------------> LAN
      ----------------------------------------
                  |
                  |
     ---------------------------------------
     QnX Target en0 (192.168.1.102)
     QnX Target wl0 (192.168.20.1)
    ----------------------------------------
                  :
                  :
      ------------------------------------
       Wifi Client (192.168.20.254)  
     --------------------------------------      

  ping from 192.168.20.254 to 192.168.1.X is working
  ping from 192.168.1.101 to 192.168.20.X is NOT working