Cisco Systems ISA550 Manual De Usuario

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Configuration Wizards
Using the Site-to-Site VPN Wizard to Configure Site-to-Site VPN
Cisco ISA500 Series Integrated Security Appliances Administration Guide
68
2
 
STEP 4
After you are finished, click Next
Configuring IKE Policies
STEP 5
Use the IKE Policies page to configure the IKE policies and to specify an IKE policy 
for the IPsec VPN policy. You can choose the default or a custom IKE policy. 
STEP 6
Click Add to add an IKE policy. 
Other options: To edit an entry, click Edit. To delete an entry, select it and click 
Delete. The default IKE policy (DefaultIke) cannot be edited or deleted. 
STEP 7
Enter the following information:
Name: Enter the name for the IKE policy. 
Encryption: Choose the algorithm used to negotiate the security 
association. There are four algorithms supported by the security appliance: 
ESP_3DES, ESP_AES_128, ESP_AES_192, and ESP_AES_256. 
HASH: Specify the authentication algorithm for the VPN header. There are 
two HASH algorithms supported by the security appliance: SHA1 and MD5. 
Ensure that the authentication algorithm is configured identically on both 
sides.
Authentication: Specify the authentication method that the security 
appliance uses to establish the identity of each IPsec peer. 
-
PRE_SHARE: Use a simple, password-based key to authenticate. The 
alpha-numeric key is shared with IKE peer. Pre-shared keys do not scale 
well with a growing network but are easier to set up in a small network. 
-
RSA_SIG: Use a digital certificate to authenticate. RSA_SIG is a digital 
certificate with keys generated by the RSA signatures algorithm. In this 
case, a certificate must be configured in order for the RSA-Signature to 
work. 
D-H Group: Choose the Diffie-Hellman group identifier. The identifier is used 
by two IPsec peers to derive a shared secret without transmitting it to each 
other. The D-H Group sets the strength of the algorithm in bits. The default is 
Group 5. The lower the Diffie-Hellman group number, the less CPU time it 
requires to be executed. The higher the D-H group number, the greater the 
security level. 
-
Group 2 (1024-bit) 
-
Group 5 (1536-bit)