A25. When Do I Need Ddns Service; A26. What Ddns Servers Does The Zywall Support; A27. What Is Ddns Wildcard; A28. Does The Zywall Support Ddns Wildcard - ZyXEL Communications ZyWall 35 Support Notes

ZyWALL 35 Support Notes
name for your web server (i.e., www.zyxel.com.tw) is still usable.

A25. When do I need DDNS service?

When you want your internal server to be accessed by using DNS name rather than using the dynamic IP
address we can use the DDNS service. The DDNS server allows to alias a dynamic IP address to a static
hostname. Whenever the ISP assigns you a new IP, the ZyWALL sends this IP to the DDNS server for its
updates.

A26. What DDNS servers does the ZyWALL support?

The DDNS servers the ZyWALL supports currently is WWW.DYNDNS.ORG where you apply the DNS from
and update the WAN IP to.

A27. What is DDNS wildcard?

Some DDNS servers support the wildcard feature which allows the hostname, *.yourhost.dyndns.org, to be
aliased to the same IP address as yourhost.dyndns.org. This feature is useful when there are multiple servers
inside and you want users to be able to use things such as www.yourhost.dyndns.org and still reach your
hostname.

A28. Does the ZyWALL support DDNS wildcard?

Yes, the ZyWALL supports DDNS wildcard that WWW.DynDNS.ORG supports. When using wildcard, you
simply enter yourhost.dyndns.org in the Host field in Network/WAN/DDNS menu.
A29. Can the ZyWALL NAT handle IPSec packets sent by the VPN gateway behind
ZyWALL?
Yes, the ZyWALL's NAT can handle IPSec ESP Tunneling mode. We know when packets go through NAT,
NAT will change the source IP address and source port for the host. To pass IPSec packets, NAT must
understand the ESP packet with protocol number 50, replace the source IP address of the IPSec gateway to the
router's WAN IP address. However, NAT should not change the source port of the UDP packets which are used
for key managements. Because the remote gateway checks this source port during connections, the port thus is
not allowed to be changed.

A30. How do I setup my ZyWALL for routing IPSec packets over NAT?

For outgoing IPSec tunnels, no extra setting is required. For forwarding the inbound IPSec ESP tunnel, A
'Default' server set in menu 15 is required. It is because NAT makes your LAN appear as a single machine to
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