User's Manual

Chapter 24 IPSec VPN
ISG50 User’s Guide
389
You have to create (and distribute) a pre-shared key. The ISG50 and remote IPSec router use it in
the authentication process, though it is not actually transmitted or exchanged.
Note: The ISG50 and the remote IPSec router must use the same pre-shared key.
Router identity consists of ID type and content. The ID type can be domain name, IP address, or e-
mail address, and the content is a (properly-formatted) domain name, IP address, or e-mail
address. The content is only used for identification. Any domain name or e-mail address that you
enter does not have to actually exist. Similarly, any domain name or IP address that you enter does
not have to correspond to the ISG50’s or remote IPSec router’s properties.
The ISG50 and the remote IPSec router have their own identities, so both of them must store two
sets of information, one for themselves and one for the other router. Local ID type and content
refers to the ID type and content that applies to the router itself, and peer ID type and content
refers to the ID type and content that applies to the other router.
Note: The ISG50’s local and peer ID type and content must match the remote IPSec
router’s peer and local ID type and content, respectively.
For example, in Table 127 on page 389, the ISG50 and the remote IPSec router authenticate each
other successfully. In contrast, in Table 128 on page 389, the ISG50 and the remote IPSec router
cannot authenticate each other and, therefore, cannot establish an IKE SA.
It is also possible to configure the ISG50 to ignore the identity of the remote IPSec router. In this
case, you usually set the peer ID type to Any. This is less secure, so you should only use this if your
ISG50 provides another way to check the identity of the remote IPSec router (for example,
extended authentication) or if you are troubleshooting a VPN tunnel.
Additional Topics for IKE SA
This section provides more information about IKE SA.
Negotiation Mode
There are two negotiation modes--main mode and aggressive mode. Main mode provides better
security, while aggressive mode is faster.
Table 127 VPN Example: Matching ID Type and Content
ISG50 REMOTE IPSEC ROUTER
Local ID type: E-mail Local ID type: IP
Local ID content: [e-mail] Local ID content: 1.1.1.2
Peer ID type: IP Peer ID type: E-mail
Peer ID content: 1.1.1.2 Peer ID content: [e-mail]
Table 128 VPN Example: Mismatching ID Type and Content
ISG50 REMOTE IPSEC ROUTER
Local ID type: E-mail Local ID type: IP
Local ID content: [e-mail] Local ID content: 1.1.1.2
Peer ID type: IP Peer ID type: E-mail
Peer ID content: 1.1.1.20 Peer ID content: [e-mail]