Chapter 20 IPSec VPN

Table 119 VPN > IPSec VPN > VPN Gateway > Edit (continued)

LABEL

DESCRIPTION

Encryption

Select which key size and encryption algorithm to use in the IKE SA. Choices are:

 

DES - a 56-bit key with the DES encryption algorithm

 

3DES - a 168-bit key with the DES encryption algorithm

 

AES128 - a 128-bit key with the AES encryption algorithm

 

AES192 - a 192-bit key with the AES encryption algorithm

 

AES256 - a 256-bit key with the AES encryption algorithm

 

The ZyWALL and the remote IPSec router must use the same key size and

 

encryption algorithm. Longer keys require more processing power, resulting in

 

increased latency and decreased throughput.

 

 

Authentication

Select which hash algorithm to use to authenticate packet data in the IPSec SA.

 

Choices are SHA1 and MD5. SHA1 is generally considered stronger than MD5,

 

but it is also slower.

 

The remote IPSec router must use the same authentication algorithm.

 

 

Add icon

This column contains icons to add and remove proposals.

 

To add a proposal, click the Add icon at the top of the column.

 

To remove a proposal, click the Remove icon next to the proposal. The ZyWALL

 

confirms that you want to delete the proposal before doing so.

 

 

Key Group

Select which Diffie-Hellman key group (DHx) you want to use for encryption keys.

 

Choices are:

 

DH1 - use a 768-bit random number

 

DH2 - use a 1024-bit random number

 

DH5 - use a 1536-bit random number

 

The longer the key, the more secure the encryption, but also the longer it takes to

 

encrypt and decrypt information. Both routers must use the same DH key group.

 

 

NAT Traversal

Select this if any of these conditions are satisfied.

 

• This IKE SA might be used to negotiate IPSec SA that use active protocol AH.

 

• There are one or more NAT routers between the ZyWALL and remote IPSec

 

router, and these routers do not support IPSec pass-thru or a similar feature.

 

The remote IPSec router must also enable NAT traversal, and the NAT routers

 

have to forward packets with UDP port 500 and UDP 4500 headers unchanged.

 

 

Dead Peer

Select this check box if you want the ZyWALL to make sure the remote IPSec

Detection

router is there before it transmits data through the IKE SA. If there has been no

(DPD)

traffic for at least 15 seconds, the ZyWALL sends a message to the remote IPSec

 

server. If the remote IPSec server responds, the ZyWALL transmits the data. If

 

the remote IPSec server does not respond, the ZyWALL shuts down the IKE SA.

 

 

More Settings/

Click this button to show or hide the Extended Authentication fields.

Less Settings

 

 

 

Extended

When multiple IPSec routers use the same VPN tunnel to connect to a single

Authentication

VPN tunnel (telecommuters sharing a tunnel for example), use extended

 

authentication to enforce a user name and password check. This way even

 

though they all know the VPN tunnel’s security settings, each still has to provide a

 

unique user name and password.

 

 

Enable Extended

Select this if one of the routers (the ZyWALL or the remote IPSec router) verifies a

Authentication

user name and password from the other router using the local user database and/

 

or an external server.

 

 

Server Mode

Select this if the ZyWALL authenticates the user name and password from the

 

remote IPSec router. You also have to select the authentication method, which

 

specifies how the ZyWALL authenticates this information.

 

 

Client Mode

Select this radio button if the ZyWALL provides a username and password to the

 

remote IPSec router for authentication. You also have to provide the User Name

 

and the Password.

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ZyWALL USG 100/200 Series User’s Guide