Guides to set Dial-on-Demand for RedHat 6.1 (and above?)
Thanks to Adzmely Mansor [doubt@ihsan.com]
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1) echo "1" > /proc/sys/net/ipv4/ip_dynaddr

2) edit /etc/ppp/options
   
   /dev/ttyS0  #com1
   demand
   idle 600    #10 minutes
   ipcp-accept-local
   ipcp-accept-remote
   noauth
   modem 115200 crtscts
   user [id]  #for PAP
   defaultroute
   noipdefault
   connect "chat -f /etc/sysconfig/network-scripts/chat-ppp0"

3) edit /etc/ppp/pap-secrets
   
   [id]    *   [password]

4) insert 1 line in rc.local
 
   pppd 1.1.1.1:1.1.1.2

5) edit /etc/conf.modules
 
   alias ppp_compress_21 ppp_deflate
   alias ppp_compress_24 ppp_deflate
   alias ppp_compress_26 bsd_comp
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