User`s guide

Chapter 10 IPSec VPN Config Screens
LAN-Cell 2 User’s Guide
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Figure 149 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.
Authentication
Before the LAN-Cell and remote IPSec router establish an IKE SA, they have to verify each
other’s identity. This process is based on pre-shared keys and router identities.
In main mode, the LAN-Cell and remote IPSec router authenticate each other in steps 5 and 6,
as illustrated below. Their identities are encrypted using the encryption algorithm and
encryption key the LAN-Cell and remote IPSec router selected in previous steps.
Figure 150 IKE SA: Main Negotiation Mode, Steps 5 - 6: Authentication
The LAN-Cell and remote IPSec router use a pre-shared key in the authentication process,
though it is not actually transmitted or exchanged.
" The LAN-Cell and the remote IPSec router must use the same pre-shared key.
Router identity consists of ID type and ID content. The ID type can be IP address, domain
name, or e-mail address, and the ID content is a specific IP address, domain name, or e-mail
address. The ID content is only used for identification; the IP address, domain name, or e-mail
address that you enter does not have to actually exist.
The LAN-Cell and the remote IPSec router each has its own identity, so each one must store
two sets of information, one for itself and one for the other router. Local ID type and ID
content refers to the ID type and ID content that applies to the router itself, and peer ID type
and ID content refers to the ID type and ID content that applies to the other router in the IKE
SA.