TMS zl Management and Configuration Guide ST.1.1.100226

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Virtual Private Networks
Configure a GRE over IPsec VPN with IKE
Figure 7-222. Add IPsec Policy Window—Step 2 of 4
11. For Key Exchange Method, keep the default, Auto (with IKEv1).
12. For IKEv1 Policy, select a previously configured IKEv1 policy.
Select the IKEv1 policy that specifies the remote tunnel endpoint as the
remote gateway.
13. Optionally, select the Enable PFS (Perfect Forward Secrecy) for keys check
box, which forces the tunnel endpoints to generate new keys for the IPsec
SA. In the list that is displayed, select one of the following:
• Group 1 (768)
• Group 2 (1024)
• Group 5 (1536)
The group determines the length of the prime number used during the
exchange. The larger the number, the more secure the key generated by
the exchange. You must match the settings on the remote tunnel endpoint.