ZyXEL Communications NWD-210N - FOR MAC V1.00 Guide de l'utilisateur télécharger pdf (Page 134)

Chapter 18 IPSec VPN

NBG5715 User’s Guide

134

18.5.2 Manual Key Setup

Manual key management is useful if you have problems with IKE key management.

18.5.2.1 Security Parameter Index (SPI)

An SPI is used to distinguish different SAs terminating at the same destination and using the same

IPSec protocol. This data allows for the multiplexing of SAs to a single gateway. The SPI (Security

Parameter Index) along with a destination IP address uniquely identify a particular Security

Association (SA). The SPI is transmitted from the remote VPN gateway to the local VPN gateway.

The local VPN gateway then uses the network, encryption and key values that the administrator

associated with the SPI to establish the tunnel.

Key Group You must choose a key group for phase 1 IKE setup. DH1 refers to Diffie-

Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman Group

2 a 1024 bit (1Kb) random number.

Phase 2

Encapsulation

Mode

Select Tunnel mode or Transport mode from the drop-down list box.

IPSec Protocol Select the security protocols used for an SA.

Both AH and ESP increase processing requirements and communications

latency (delay).

If you select ESP here, you must select options from the Encryption

Algorithm and Authentication Algorithm fields (described below).

Encryption

Algorithm

Select which key size and encryption algorithm to use for data communications.

Choices are:

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

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

The NBG5715 and the remote IPSec router must use the same algorithms and

key , which can be used to encrypt and decrypt the message or to generate and

verify a message authentication code. Longer keys require more processing

power, resulting in increased latency and decreased throughput.

Authentication

Algorithm

Select which hash algorithm to use to authenticate packet data. Choices are

SHA1 and MD5. SHA1 is generally considered stronger than MD5, but it is also

slower.

SA Life Time Define the length of time before an IKE or IPSec SA automatically renegotiates

in this field. It may range from 1 to 2,000,000,000 seconds.

A short SA Life Time increases security by forcing the two VPN gateways to

update the encryption and authentication keys. However, every time the VPN

tunnel renegotiates, all users accessing remote resources are temporarily

disconnected.

Key Group You must choose a key group for phase 1 IKE setup. DH1 refers to Diffie-

Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman Group

2 a 1024 bit (1Kb) random number.

Back Click Back to return to the previous screen.

Apply Click Apply to save your changes back to the NBG5715.

Cancel Click Cancel to restore your previous settings.

Table 54 Security > IPSec VPN > General > Edit: IKE (continued)

LABEL DESCRIPTION

1 2 ... 129 130 131 132 133 134 135 136 137 138 139 ... 291 292

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