WESM zl Management and Configuration Guide WT.01.28 and greater

6-40
IP Services—IP Settings, DHCP, and DNS
DHCP Server
Figure 6-27. Specifying the Value for an Extended Option
5. Click the Name field. It turns into a drop-down menu that includes the names of
all of the options defined globally. (See “Setting Up Global Options” on
page 6-37.)
6. In the Value field, enter either an IP address or an alphanumeric string, depending
on whether the type specified for the global option is ip or ascii. The Wireless
Edge Services zl Module sends this value for the option to DHCP clients.
7. Click the Insert button again to configure another option. You can configure as
many options as have been defined globally.
8. Click the OK button.
9. Click the Save link at the top of the Web browser interface to save the changes
to the startup-config.
Configuring Dynamic DNS (DDNS)
A DNS server resolves hostnames to IP addresses. For the DNS server to function
correctly, clearly its table must include the correct IP address for each hostname.
However, a device that acts as a DHCP client might unexpectedly receive a new IP
address, invalidating the DNS server’s hostname table. DDNS addresses this problem
by updating a DNS server whenever a client’s IP address changes.
The Wireless Edge Services zl Module supports DDNS as part of its function as a
DHCP server. The module can either update the DNS server itself or allow clients to
do so. The DNS server itself, of course, must also support DDNS (as specified in
Request for Comments [RFC] 2136). Such a server is called a DDNS server. In
addition, if the clients will send the updates, they must also support DDNS.