> ISAKMP Configuration Mode Commands
> The ISAKMP Configuration Mode is used to configure Internet Security Association Key Management Protocol (ISAKMP) policies that are used to define Internet Key Exchange (IKE) security associations (SAs).
> Modification(s) to an existing ISAKMP policy configuration will not take effect until the related security association has been cleared. Refer to the clear crypto security-association command located in the Exec Mode Commands chapter of the Command Line Interface Reference for more information.
> Important: The commands or keywords/variables that are available are dependent on platform type, product version, and installed license(s).
> authentication
> Configures the ISAKMP policy authentication mode.
> Product
> PDSN, HA, GGSN
> Privilege
> Security Administrator, Administrator
> Syntax
> authentication preshared-key
> [ default | no ] authentication
> default
> Restores the default setting of this parameter. The command is enabled by default.
> no
> Disables the preshared key authentication mode.
> preshared-key
> Specifies that the policy will be authenticated through the use of the pre-shared key.
> Usage
> When the system is configured to use ISAKMP-type crypto maps for establishing IPSec tunnels, this command is used to indicate that the policy will be authenticated through the use of the pre-shared key configured in the ISAKMP crypto map.
> Example
> The following command sets policy authentication mode to use a pre-shared key:
> authentication preshared-key
> encryption
> Configures the encryption protocol to use to protect subsequent IKE SA negotiations.
> Product
> PDSN, HA, GGSN
> Privilege
> Security Administrator, Administrator
> Syntax
> encryption { 3des-cbc | aes-cbc-128 | aes-cbc-256 | des-cbc }
> [ default | no ] encryption
> default
> Restores the default setting of this parameter.
> no
> Removes a previously configured encryption type.
> 3des-cbc
> Specifies that the encryption protocol is Triple Data Encryption Standard (3DES) in chain block (CBC) mode.
> aes-cbc-128
> Specifies that the encryption protocol is Advanced Encryption Standard (AES) in CBC mode with a 128-bit key.
> aes-cbc-256
> Specifies that the encryption protocol is Advanced Encryption Standard (AES) in CBC mode with a 256-bit key.
> des-cbc
> Specifies that the encryption protocol is DES in CBC mode. This is the default setting.
> Usage
> Once the D-H exchange between the system and the security gateway has been successfully completed, subsequent IKE SA negotiations will be protected using the protocol specified by this command.
> Example
> The following command sets the IKE encryption method to 3des-cbc:
> encryption 3des-cbc
> end
> Exits the current configuration mode and returns to the Exec mode.
> Product
> PDSN, HA, GGSN
> Privilege
> Security Administrator, Administrator
> Syntax
> end
> Usage
> Returns to the Exec mode.
> exit
> Exits the current configuration mode and returns to the Context configuration mode.
> Product
> PDSN, HA, GGSN
> Privilege
> Security Administrator, Administrator
> Syntax
> exit
> Usage
> Return to the Context Configuration mode.
> group
> Configures the Oakely group (also known as the Diffie-Hellman (D-H ) group) in which the D-H exchange occurs.
> Product
> PDSN, HA, GGSN
> Privilege
> Security Administrator, Administrator
> Syntax
> group { 1 | 2 | 5 }
> [ default | no ] group
> default
> Restores the default setting of this parameter.
> no
> Removes a previously configured group.
> { 1 | 2 | 5 }
> Default: 1
> The number of the Oakley group. The following groups are allowed:

> • | 1 : Enables Oakley Group 1 using a 768-bit modp as defined in RFC 2409.

> • | 2 : Enables Oakley Group 2, using a 1024-bit modp as defined in RFC 2409.

> • | 5 : Enables Oakley Group 5, using a 1536-bit modp as defined in RFC 3526.

> Usage
> Specifies the Oakley group that determine the length of the base prime numbers that are used during the key exchange process.
> Example
> The following command sets the group to 5 which specifies 1536-bit base prime numbers:
> group 5
> hash
> Configures the IKE hash protocol to use during IKE SA negotiations.
> Product
> PDSN, HA, GGSN
> Privilege
> Security Administrator, Administrator\
> Syntax
> hash { md5 | sha1 }
> [ default | no ] hash
> default
> Restores the default setting of this parameter.
> no
> Removes a previously configured hash algorithm.
> md5
> Specifies that the hash protocol is Message Digest 5 truncated to 96 bits.
> sha1
> Specifies that the hash protocol is Secure Hash Algorithm-1 truncated to 96 bits. This is the default setting for this command.
> Usage
> Use this command to configure the hash algorithm used during key negotiation.
> Example
> Set the hash algorithm to Message-Digest 5 by entering the following command:
> hash md5
> lifetime
> Configures the lifetime of the IKE Security Association (SA).
> Product
> PDSN, HA, GGSN
> Privilege
> Security Administrator, Administrator
> Syntax
> lifetime seconds
> default lifetime
> default
> Restores the default setting of this parameter.
> seconds
> Default: 86400
> The number of seconds for the SA to live. seconds must be an integer from 60 to 86400.
> Usage
> Use this command to set the time that an ISAKMP SA will be valid. The lifetime is negotiated with the peer and the lowest configured lifetime duration is used.
> Example
> The following command sets the SA lifetime to 100 seconds:
> lifetime 100

Cisco Systems Inc.
Tel: 408-526-4000
Fax: 408-527-0883