Cisco ASA 5505 - Manual (Page 1364)

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Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 64 Configuring IPsec and ISAKMP
Configuring ISAKMP
There is an implicit trade-off between security and performance when you choose a specific value for
each parameter. The level of security the default values provide is adequate for the security requirements
of most organizations. If you are interoperating with a peer that supports only one of the values for a
parameter, your choice is limited to that value.
Note New ASA configurations do not have a default IKEv1 or IKEv2 policy.
To configure IKE policies, in global configuration mode, use the crypto ikev1 | ikev2 policy command
to enter IKE policy configuration mode:
crypto ikev1 | ikev2 policy priority
You must include the priority in each of the ISAKMP commands. The priority number uniquely
identifies the policy and determines the priority of the policy in IKE negotiations.
To enable and configure IKE, complete the following steps, using the IKEv1 examples as a guide:
Note If you do not specify a value for a given policy parameter, the default value applies.
Step 1 Enter IKEv1 policy configuration mode:
hostname(config)# crypto ikev1 policy 1
hostname(config-ikev1-policy)#
Step 2 Specify the encryption algorithm. The default is Triple DES. This example sets encryption to DES.
encryption [aes | aes-192 | aes-256 | des | 3des]
For example:
hostname(config-ikev1-policy)# encryption des
Step 3 Specify the hash algorithm. The default is SHA-1. This example configures MD5.
hash [md5 | sha]
For example:
hostname(config-ikev1-policy)# hash md5
Step 4 Specify the authentication method. The default is preshared keys. This example configures RSA
signatures.
authentication [pre-share | crack | rsa-sig]
For example:
hostname(config-ikev1-policy)# authentication rsa-sig
Step 5 Specify the Diffie-Hellman group identifier. The default is Group 2. This example configures Group 5.
group [1 | 2 | 5]
For example:
hostname(config-ikev1-policy)# group 5
Step 6 Specify the SA lifetime. This examples sets a lifetime of 4 hours (14400 seconds). The default is 86400
seconds (24 hours).
lifetime seconds