c Policy

Configuring an IPSec Policy

An IPSec policy defines a combination of security parameters (IPSec proposals) used during IPSec negotiation. It defines Perfect Forward Secrecy (PFS) and the proposals needed for the connection. During the IPSec negotiation, IPSec looks for an IPSec proposal that is the same on both peers. The peer that initiates the negotiation sends all its policies to the remote peer, and the remote peer tries to find a match.

A match is made when both policies from the two peers have a proposal that contains the same configured attributes. If the lifetimes are not identical, the shorter lifetime between the two policies (from the host and peer) is used.

You can create multiple, prioritized IPSec proposals at each peer to ensure that at least one proposal will match a remote peer's proposal. First, you configure one or more IPSec proposals first; then you associate these proposals with an IPSec policy. You can then prioritize a list of proposals used by IPSec in the policy statement by listing the proposals you want to use, from first to last.

To configure an IPSec policy, include the policy statement and specify the policy name and one or more proposals you want to associate with this policy:

 [edit security ipsec]  policy  ipsec-policy-name;  

Perfect Forward Secrecy (PFS) provides additional security by means of a Diffie-Hellman shared secret value. With PFS, if one key is compromised, previous and subsequent keys are secure because they are not derived from previous keys. To configure PFS, include the perfect-forward-secrecy statement.

 [edit security ipsec]  perfect-forward-secrecy {     keys (group1  group2); } 

The key can be one of the following:

• group1 ” IKE uses the 768-bit Diffie-Hellman prime modulus group when performing the new Diffie-Hellman exchange.

• group2 ” IKE uses the 1,024-bit Diffie-Hellman prime modulus group when performing the new Diffie-Hellman exchange. group2 provides more security than group1 , but requires more processing time.