ZyXEL NBG420N Manuel d'utilisateur télécharger pdf (Page 185)

Chapter 15 IPSec VPN

NBG420N User’s Guide

185

15.5 IPSec VPN Technical Reference

IKE SA Proposal

The IKE SA proposal is used to identify the encryption algorithm, authentication algorithm,

and Diffie-Hellman (DH) key group that the NBG420N and remote IPSec router use in the

IKE SA. In main mode, this is done in steps 1 and 2, as illustrated below.

Figure 111 IKE SA: Main Negotiation Mode, Steps 1 - 2: IKE SA Proposal

The NBG420N sends a proposal to the remote IPSec router. Each proposal consists of an

encryption algorithm, authentication algorithm, and DH key group that the NBG420N wants

to use in the IKE SA. The remote IPSec router sends the accepted proposal back to the

NBG420N. If the remote IPSec router rejects the proposal (for example, if the VPN tunnel is

not configured correctly), the NBG420N and remote IPSec router cannot establish an IKE SA.

Note: Both routers must use the same encryption algorithm, authentication algorithm,

and DH key group.

See the field descriptions for information about specific encryption algorithms, authentication

algorithms, and DH key groups. See Diffie-Hellman (DH) Key Exchange on page 185 for

more information about DH key groups.

Diffie-Hellman (DH) Key Exchange

The NBG420N and the remote IPSec router use a DH key exchange to establish a shared

secret, which is used to generate encryption keys for IKE SA and IPSec SA. In main mode, the

DH key exchange is done in steps 3 and 4, as illustrated below.

Figure 112 IKE SA: Main Negotiation Mode, Steps 3 - 4: DH Key Exchange

The DH key exchange is based on DH key groups. Each key group is a fixed number of bits

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

encrypt and decrypt information. For example, DH2 keys (1024 bits) are more secure than

DH1 keys (768 bits), but DH2 encryption keys take longer to encrypt and decrypt.

1 2 ... 180 181 182 183 184 185 186 187 188 189 190 ... 339 340

Pas de commentaire

ZyXEL NBG420N Manuel d'utilisateur Page 185