ZyXEL P-335U User Guide - Page 155
The remote IPSec router must also have NAT traversal, enabled. See, for more, information.
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P-334U/P-335U User's Guide The following table describes the labels in this screen. Table 53 Security > VPN > Rule Setup: IKE (Advanced) LABEL DESCRIPTION Property Active Select this check box to activate this VPN policy. This option determines whether a VPN rule is applied before a packet leaves the firewall. Keep Alive Select this check box to have the ZyXEL Device automatically reinitiate the SA after the SA lifetime times out, even if there is no traffic. The remote IPSec router must also have keep alive enabled in order for this feature to work. NAT Traversal Select this check box to enable NAT traversal. NAT traversal allows you to set up a VPN connection when there are NAT routers between the two IPSec routers. Note: The remote IPSec router must also have NAT traversal enabled. See Section 13.1.2.5 on page 143 for more information. IPSec Keying Mode Protocol Number Enable Replay Detection DNS Server (for IPSec VPN) Local Policy You can use NAT traversal with ESP protocol using Transport or Tunnel mode, but not with AH protocol nor with manual key management. In order for an IPSec router behind a NAT router to receive an initiating IPSec packet, set the NAT router to forward UDP ports 500 and 4500 to the IPSec router behind the NAT router. Select IKE or Manual from the drop-down list box. IKE provides more protection so it is generally recommended. Manual is a useful option for troubleshooting if you have problems using IKE key management. Enter 1 for ICMP, 6 for TCP, 17 for UDP, etc. 0 is the default and signifies any protocol. As a VPN setup is processing intensive, the system is vulnerable to Denial of Service (DoS) attacks The IPSec receiver can detect and reject old or duplicate packets to protect against replay attacks. Select YES from the drop-down menu to enable replay detection, or select NO to disable it. If there is a private DNS server that services the VPN, type its IP address here. The ZyXEL Device assigns this additional DNS server to the ZyXEL Device's DHCP clients that have IP addresses in this IPSec rule's range of local addresses. A DNS server allows clients on the VPN to find other computers and servers on the VPN by their (private) domain names. Local IP addresses must be static and correspond to the remote IPSec router's configured remote IP addresses. Two active SAs can have the same configured local or remote IP address, but not both. You can configure multiple SAs between the same local and remote IP addresses, as long as only one is active at any time. In order to have more than one active rule with the Secure Gateway Address field set to 0.0.0.0, the ranges of the local IP addresses cannot overlap between rules. If you configure an active rule with 0.0.0.0 in the Secure Gateway Address field and the LAN's full IP address range as the local IP address, then you cannot configure any other active rules with the Secure Gateway Address field set to 0.0.0.0. Chapter 13 IPSec VPN 155