L2TP with MPPE

For my understanding L2TP usually use IPsec for security, but today I tested a cpe router which has a L2TP client which use MPPE. I was puzzled but then I figured out that CISCO ios support L2TP with MPPE. You just need to add the line "ppp encrypt mppe auto" to the virtual template,

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vpdn-group L2TP-pure

 accept-dialin

  protocol l2tp

  virtual-template 52

interface Virtual-Template52

 ip unnumbered Loopback1

 ip nat inside

 ip virtual-reassembly

 peer default ip address pool L2TP-POOL

ppp encrypt mppe auto

ip local pool L2TP-POOL 192.168.60.10 192.168.60.100

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