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Recovery Interval

When the ZyXEL Device is using a lower priority connection (usually a WAN

backup connection), it periodically checks to whether or not it can use a higher

priority connection.

Type the number of seconds (30 recommended) for the ZyXEL Device to wait

between checks. Allow more time if your destination IP address handles lots of

traffic.

Timeout

Type the number of seconds (3 recommended) for your ZyXEL Device to wait for a

ping response from one of the IP addresses in the

Check WAN IP Address

field

before timing out the request. The WAN connection is considered "down" after the

ZyXEL Device times out the number of times specified in the

Fail Tolerance

field.

Use a higher value in this field if your network is busy or congested.

Traffic Redirect

Traffic redirect forwards traffic to a backup gateway when the ZyXEL Device

cannot connect to the Internet.

Active Traffic

Redirect

Select this check box to have the ZyXEL Device use traffic redirect if the normal

WAN connection goes down.

Note: If you activate traffic redirect, you must configure at least

one Check WAN IP Address.

Metric

This field sets this route's priority among the routes the ZyXEL Device uses.

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".

Backup Gateway

Type the IP address of your backup gateway in dotted decimal notation. The

ZyXEL Device automatically forwards traffic to this IP address if the ZyXEL

Device's Internet connection terminates.

Apply

Click

Apply

to save the changes.

Cancel

Click

Cancel

to begin configuring this screen afresh.

Table 17

WAN Backup Setup (continued)

LABEL

DESCRIPTION

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63

C

HAPTER

5

LAN Setup

This chapter describes how to configure LAN settings.

5.1

LAN Overview

A Local Area Network (LAN) is a shared communication system to which many computers are

attached. A LAN is a computer network limited to the immediate area, usually the same building or

floor of a building. The LAN screens can help you configure a LAN DHCP server and manage IP

addresses.

See

Section 5.3 on page 68

to configure the

LAN

screens.

5.1.1

LANs, WANs and the ZyXEL Device

The actual physical connection determines whether the ZyXEL Device ports are LAN or WAN ports.

There are two separate IP networks, one inside the LAN network and the other outside the WAN

network as shown next.

Figure 32

LAN and WAN IP Addresses

5.1.2

DHCP Setup

DHCP (Dynamic Host Configuration Protocol, RFC 2131 and RFC 2132) allows individual clients to

obtain TCP/IP configuration at start-up from a server. You can configure the ZyXEL Device as a

DHCP server or disable it. When configured as a server, the ZyXEL Device provides the TCP/IP

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64

configuration for the clients. If you turn DHCP service off, you must have another DHCP server on

your LAN, or else the computer must be manually configured.

5.1.2.1

IP Pool Setup

The ZyXEL Device is pre-configured with a pool of IP addresses for the DHCP clients (DHCP Pool).

See the product specifications in the appendices. Do not assign static IP addresses from the DHCP

pool to your LAN computers.

5.1.3

DNS Server Address

DNS (Domain Name System) is for mapping a domain name to its corresponding IP address and

vice versa. The DNS server is extremely important because without it, you must know the IP

address of a machine before you can access it. The DNS server addresses that you enter in the

DHCP setup are passed to the client machines along with the assigned IP address and subnet mask.

There are two ways that an ISP disseminates the DNS server addresses. The first is for an ISP to

tell a customer the DNS server addresses, usually in the form of an information sheet, when s/he

signs up. If your ISP gives you the DNS server addresses, enter them in the

DNS Server

fields in

DHCP Setup

, otherwise, leave them blank.

Some ISP’s choose to pass the DNS servers using the DNS server extensions of PPP IPCP (IP

Control Protocol) after the connection is up. If your ISP did not give you explicit DNS servers,

chances are the DNS servers are conveyed through IPCP negotiation. The ZyXEL Device supports

the IPCP DNS server extensions through the DNS proxy feature.

If the

Primary

and

Secondary DNS Server

fields in the

DHCP Setup

screen are not

specified, for

instance, left as

0.0.0.0

, the ZyXEL Device tells the DHCP clients that it itself is the DNS server.

When a computer sends a DNS query to the ZyXEL Device, the ZyXEL Device forwards the query to

the real DNS server learned through IPCP and relays the response back to the computer.

Please note that DNS proxy works only when the ISP uses the IPCP DNS server extensions. It does

not mean you can leave the DNS servers out of the DHCP setup under all circumstances.

If your

ISP gives you explicit DNS servers, make sure that you enter their IP addresses in the

DHCP Setup

screen. This way, the ZyXEL Device can pass the DNS servers to the computers and the computers

can query the DNS server directly without the ZyXEL Device’s intervention.

5.1.4

DNS Server Address Assignment

Use DNS (Domain Name System) to map a domain name to its corresponding IP address and vice

versa. The DNS server is extremely important because without it, you must know the IP address of

a computer before you can access it.

There are two ways that an ISP disseminates the DNS server addresses.

•

The ISP tells you the DNS server addresses, usually in the form of an information sheet, when

you sign up. If your ISP gives you DNS server addresses, enter them in the DNS Server fields in

the

DHCP Setup

screen.

•

The ZyXEL Device acts as a DNS proxy when the

Primary

and

Secondary DNS Server

fields

are left as

0.0.0.0

in the

DHCP Setup

screen.

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5.2

LAN TCP/IP

The ZyXEL Device has built-in DHCP server capability that assigns IP addresses and DNS servers to

systems that support DHCP client capability.

5.2.1

IP Address and Subnet Mask

Similar to the way houses on a street share a common street name, so too do computers on a LAN

share one common network number.

Where you obtain your network number depends on your particular situation. If the ISP or your

network administrator assigns you a block of registered IP addresses, follow their instructions in

selecting the IP addresses and the subnet mask.

If the ISP did not explicitly give you an IP network number, then most likely you have a single user

account and the ISP will assign you a dynamic IP address when the connection is established. If this

is the case, it is recommended that you select a network number from 192.168.0.0 to

192.168.255.0 and you must enable the Network Address Translation (NAT) feature of the ZyXEL

Device. The Internet Assigned Number Authority (IANA) reserved this block of addresses

specifically for private use; please do not use any other number unless you are told otherwise. Let's

say you select 192.168.1.0 as the network number; which covers 254 individual addresses, from

192.168.1.1 to 192.168.1.254 (zero and 255 are reserved). In other words, the first three numbers

specify the network number while the last number identifies an individual computer on that

network.

Once you have decided on the network number, pick an IP address that is easy to remember, for

instance, 192.168.1.1, for your ZyXEL Device, but make sure that no other device on your network

is using that IP address.

The subnet mask specifies the network number portion of an IP address. Your ZyXEL Device will

compute the subnet mask automatically based on the IP address that you entered. You don't need

to change the subnet mask computed by the ZyXEL Device unless you are instructed to do

otherwise.

5.2.1.1

Private IP Addresses

Every machine on the Internet must have a unique address. If your networks are isolated from the

Internet, for example, 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:

• 10.0.0.0

— 10.255.255.255

• 172.16.0.0

— 172.31.255.255

•

192.168.0.0 — 192.168.255.255

You can obtain your IP address from the IANA, from an ISP or it can be assigned from a private

network. If you belong to a small organization and your Internet access is through an ISP, the ISP

can provide you with the Internet addresses for your local networks. On the other hand, if you are

part of a much larger organization, you should consult your network administrator for the

appropriate IP addresses.