Chapter 6 Wan Screens; Wan Overview; Tcp/Ip Priority (Metric); Wan Ip Address Assignment - ZyXEL Communications Internet Security Gateway ZyWALL 2 Series User Manual

6.1

WAN Overview

See the LAN chapter for information about Primary and Secondary DNS Server,
DNS Server Address Assignment and IP Address and Subnet Mask.
6.2

TCP/IP Priority (Metric)

The metric represents the "cost of transmission". A router determines the best route for transmission by
choosing a path with the lowest "cost". RIP routing uses hop count as the measurement of cost, with a
minimum of "1" for directly connected networks. The number must be between "1" and "15"; a number
greater than "15" means the link is down. The smaller the number, the lower the "cost".
The metric sets the priority for the ZyWALL's routes to the Internet. If any two of the default routes have the
same metric, the ZyWALL uses the following pre-defined priorities
1. WAN: designated by the ISP (see section 6.6) or a static route (see the IP Static Route Setup chapter)
2. Traffic Redirect (see section 6.9)
3. Dial Backup (see section 6.10)
For example, if WAN has a metric of "1" and Traffic Redirect has a metric of "2" and Dial Backup has a
metric of "3", the WAN connection acts as the primary default route. If the WAN route fails to connect to the
Internet, the ZyWALL tries Traffic Redirect next. In the same manner, the ZyWALL uses Dial Backup if
Traffic Redirect also fails.
If you want Dial Backup to take first priority over Traffic Redirect or even WAN, all you need to do is set
Dial Backup's metric to "1" and the others to "2" (or greater).
6.3

WAN IP Address Assignment

Every computer on the Internet must have a unique IP address. If your networks are isolated from the
Internet, for instance, only between your two branch offices, you can assign any IP addresses to the hosts
without problems. However, the Internet Assigned Numbers Authority (IANA) has reserved the following
three blocks of IP addresses specifically for private networks.
WAN Screens
This chapter describes how to configure WAN settings.
ZyWALL 2 Series User's Guide
Chapter 6
WAN Screens
6-1