Chapter 30 IPSec VPN
UAG5100 User’s Guide
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enter does not have to actually exist. Similarly, any domain name or IP address that you enter does
not have to correspond to the UAG’s or remote IPSec router’s properties.
The UAG 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 UAG’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
, the UAG and the remote IPSec router authenticate each
other successfully. In contrast, in
, the UAG and the remote IPSec router
cannot authenticate each other and, therefore, cannot establish an IKE SA.
It is also possible to configure the UAG 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
UAG 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.
Main mode takes six steps to establish an IKE SA.
Steps 1 - 2: The UAG sends its proposals to the remote IPSec router. The remote IPSec router
selects an acceptable proposal and sends it back to the UAG.
Steps 3 - 4: The UAG and the remote IPSec router exchange pre-shared keys for authentication
and participate in a Diffie-Hellman key exchange, based on the accepted DH key group, to establish
a shared secret.
Table 135
VPN Example: Matching ID Type and Content
UAG
REMOTE IPSEC ROUTER
Local ID type: E-mail
Local ID type: IP
Local ID content: tom@yourcompany.com
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: tom@yourcompany.com
Table 136
VPN Example: Mismatching ID Type and Content
UAG
REMOTE IPSEC ROUTER
Local ID type: E-mail
Local ID type: IP
Local ID content: tom@yourcompany.com
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: tom@yourcompany.com
