Negotiation Mode; Keep Alive; Remote Dns Server - ZyXEL Communications P-2612HW-F1 User Manual

• Set the IPSec SA lifetime. This field allows you to determine how long the IPSec
SA should stay up before it times out. The ZyXEL Device automatically
renegotiates the IPSec SA if there is traffic when the IPSec SA lifetime period
expires. The ZyXEL Device also automatically renegotiates the IPSec SA if both
IPSec routers have keep alive enabled, even if there is no traffic. If an IPSec SA
times out, then the IPSec router must renegotiate the SA the next time
someone attempts to send traffic.

14.9.6 Negotiation Mode

The phase 1 Negotiation Mode you select determines how the Security
Association (SA) will be established for each connection through IKE negotiations.
• Main Mode ensures the highest level of security when the communicating
parties are negotiating authentication (phase 1). It uses 6 messages in three
round trips: SA negotiation, Diffie-Hellman exchange and an exchange of
nonces (a nonce is a random number). This mode features identity protection
(your identity is not revealed in the negotiation).
• Aggressive Mode is quicker than Main Mode because it eliminates several
steps when the communicating parties are negotiating authentication (phase 1).
However the trade-off is that faster speed limits its negotiating power and it
also does not provide identity protection. It is useful in remote access situations
where the address of the initiator is not know by the responder and both parties
want to use pre-shared key authentication.

14.9.7 Keep Alive

When you initiate an IPSec tunnel with keep alive enabled, the ZyXEL Device
automatically renegotiates the tunnel when the IPSec SA lifetime period expires
(see Section 14.9.5 on page 284
IPSec tunnel becomes an "always on" connection after you initiate it. Both IPSec
routers must have a ZyXEL Device-compatible keep alive feature enabled in order
for this feature to work.
If the ZyXEL Device has its maximum number of simultaneous IPSec tunnels
connected to it and they all have keep alive enabled, then no other tunnels can
take a turn connecting to the ZyXEL Device because the ZyXEL Device never drops
the tunnels that are already connected.
When there is outbound traffic with no inbound traffic, the ZyXEL Device
automatically drops the tunnel after two minutes.

14.9.8 Remote DNS Server

In cases where you want to use domain names to access Intranet servers on a
remote network that has a DNS server, you must identify that DNS server. You
P-2612HW-F1 User's Guide
for more on the IPSec SA lifetime). In effect, the
Chapter 14 VPN
285