ZyXEL Communications P-334W User Manual

Prestige 334W User’s Guide 

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16-7 

 Use ESP security protocol (in either transport or tunnel mode). 

 Use IKE keying mode. 

 Enable NAT traversal on both IPSec endpoints. 

In order for IPSec router A (see the figure) to receive an initiating IPSec packet from IPSec router B, set the 
NAT router to forward UDP port 500 to IPSec router A. 

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 cannot use DNS servers on the LAN or from the ISP 
since these DNS servers cannot resolve domain names to private IP addresses on the remote network 

The following figure depicts an example where three VPN tunnels are created from Prestige A; one to 
branch office 2, one to branch office 3 and another to headquarters. In order to access computers that use 
private domain names on the headquarters (HQ) network, the Prestige at branch office 1 uses the Intranet 
DNS server in headquarters. The DNS server feature for VPN does not work with Windows 2000 or 
Windows XP.