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N600 Wireless Dual Band Gigabit Router Premium Edition WNDR3800

WAN Setup

The WAN Setup screen lets you configure a DMZ (demilitarized zone) server, change the

Maximum Transmit Unit (MTU) size, and enable the router to respond to a ping on the WAN

(Internet) port. Select

Advanced > Setup > WAN Setup

to view the following screen:

•

Disable Port Scan and DoS Protection

. DoS protection protects your LAN against

Denial of Service attacks such as Syn flood, Smurf Attack, Ping of Death, Teardrop

Attack, UDP Flood, ARP Attack, Spoofing ICMP, Null Scan, and many others. This should

be disabled only in special circumstances.

•

Default DMZ Server

. This feature is sometimes helpful when you are playing online

games and/or videoconferencing. Be careful when using this feature because it makes

the firewall security less effective. See the following section,

Default DMZ Server

for

more details.

•

Respond to Ping on Internet Port

. If you want the router to respond to a ping from the

Internet, select this check box. Use this only as a diagnostic tool because it allows your

router to be discovered. Do not select this check box unless you have a specific reason.

•

Disable IGMP Proxying

. IGMP proxying allows a computer on the local area network

(LAN) to receive the multicast traffic it is interested in from the Internet. You can select

this check box to disable the feature if you do not need it.

•

MTU Size (in bytes)

. The normal MTU (Maximum Transmit Unit) value for most Ethernet

networks is 1500 bytes, or 1492 bytes for PPPoE connections. For some ISPs you might

need to reduce the MTU. This is rarely required, and should not be done unless you are

sure it is necessary for your ISP connection. See

Change the MTU Size

on page 37.

•

NAT Filtering

. Network Address Translation (NAT) determines how the router processes

inbound traffic. Secured NAT provides a secured firewall to protect the computers on the

LAN from attacks from the Internet, but might prevent some Internet games, point-to-point

applications, or multimedia applications from functioning. Open NAT provides a much

less secured firewall, but allows almost all Internet applications to function.

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Default DMZ Server

The default DMZ server feature is helpful when you are using some online games and

videoconferencing applications that are incompatible with Network Address Translation

(NAT). The router is programmed to recognize some of these applications and to work

correctly with them, but there are other applications that might not function well. In some

cases, one local computer can run the application correctly if that computer’s IP address is

entered as the default DMZ server.

WARNING!

DMZ servers pose a security risk. A computer designated as the

default DMZ server loses much of the protection of the firewall

and is exposed to exploits from the Internet. If compromised, the

DMZ server computer can be used to attack other computers on

your network.

Incoming traffic from the Internet is usually discarded by the router unless the traffic is a

response to one of your local computers or a service that you have configured in the Port

Forwarding/Port Triggering screen. Instead of discarding this traffic, you can have it

forwarded to one computer on your network. This computer is called the default DMZ server.



To set up a default DMZ server, do the following:

1.

On the WAN Setup screen, select the

Default DMZ Server

check box.

2.

Type the IP address.

3.

Click

Apply

.

Change the MTU Size

The Maximum Transmission Unit (MTU) is the largest data packet a network device

transmits. When one network device communicates across the Internet with another, the data

packets travel through many devices along the way. If any device in the data path has a lower

MTU setting than the other devices, the data packets has to be split or “fragmented” to

accommodate the one with the smallest MTU.

The best MTU setting for NETGEAR equipment is often just the default value, and changing

the value might fix one problem but cause another. Leave MTU unchanged unless one of

these situations occurs:

•

You have problems connecting to your ISP or other Internet service, and the technical

support of either the ISP or NETGEAR recommends changing the MTU setting. These

web-based applications might require an MTU change:

-

A secure website that won’t open, or displays only part of a Web page

-

Yahoo email

-

MSN portal

-

America Online’s DSL service

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•

You use VPN and have severe performance problems.

•

You used a program to optimize MTU for performance reasons, and now you have

connectivity or performance problems.

Note:

An incorrect MTU setting can cause Internet communication

problems such as the inability to access certain Web sites, frames

within Web sites, secure login pages, or FTP or POP servers.

If you suspect an MTU problem, a common solution is to change the MTU to 1400. If you are

willing to experiment, you can gradually reduce the MTU from the maximum value of 1500

until the problem goes away. The following table describes common MTU sizes and

applications.

Table 2.

Common MTU Sizes

MTU

Application

1500

The largest Ethernet packet size and the default value. This is the typical setting for

non-PPPoE, non-VPN connections, and is the default value for NETGEAR routers,

adapters, and switches.

1492

Used in PPPoE environments.

1472

Maximum size to use for pinging. (Larger packets are fragmented.)

1468

Used in some DHCP environments.

1460

Usable by AOL if you do not have large email attachments, for example.

1436

Used in PPTP environments or with VPN.

1400

Maximum size for AOL DSL.

576

Typical value to connect to dial-up ISPs.



To change the MTU size:

1.

Select

Advanced > Setup > WAN Setup

.

2.

In the MTU Size field, enter a new size between 64 and 1500.

3.

Click

Apply

to save the settings.

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LAN Setup

The LAN Setup screen allows configuration of LAN IP services such as Dynamic Host

Configuration Protocol (DHCP) and Routing Information Protocol (RIP).

The router is shipped preconfigured to use private IP addresses on the LAN side and to act

as a DHCP server. The router’s default LAN IP configuration is:

•

LAN IP address:

192.168.1.1

•

Subnet mask:

255.255.255.0

These addresses are part of the designated private address range for use in private networks

and should be suitable for most applications. If your network has a requirement to use a

different IP addressing scheme, you can make those changes in the LAN Setup screen.



To change the LAN settings:

Note:

If you change the LAN IP address of the router while connected

through the browser, you will be disconnected. You will have to open

a new connection to the new IP address and log in again.

1.

Select

Advanced > Setup > LAN Setup

to display the following screen:

2.

Enter the settings that you want to customize. These settings are described in the following

section,

LAN Setup Screen Settings

.

3.

Click

Apply

to save your changes.

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LAN Setup Screen Settings

LAN TCP/IP Setup

•

IP Address

. The LAN IP address of the router.

•

IP Subnet Mask

. The LAN subnet mask of the router. Combined with the IP address, the

IP subnet mask allows a device to know which other addresses are local to it, and which

have to be reached through a gateway or router.

•

RIP Direction

. Router Information Protocol (RIP) allows a router to exchange routing

information with other routers. This setting controls how the router sends and receives

RIP packets. Both is the default setting. With the Both or Out Only setting, the router

broadcasts its routing table periodically. With the Both or In Only setting, the router

incorporates the RIP information that it receives.

•

RIP Version

. This controls the format and the broadcasting method of the RIP packets

that the router sends. It recognizes both formats when receiving. By default, the RIP

function is disabled.

RIP-1

is universally supported. It is adequate for most networks, unless you have an

unusual network setup.

RIP-2

carries more information. Both RIP-2B and RIP-2M send the routing data in RIP-2

format. RIP-2B uses subnet broadcasting. RIP-2M uses multicasting.

Use Router as a DHCP Server

This check box is usually selected so that the router functions as a Dynamic Host

Configuration Protocol (DHCP) server.

•

Starting IP Address

. Specify the start of the range for the pool of IP addresses in the

same subnet as the router.

•

Ending IP Address

. Specify the end of the range for the pool of IP addresses in the

same subnet as the router.

Address Reservation

When you specify a reserved IP address for a computer on the LAN, that computer receives

the same IP address each time it accesses the router’s DHCP server. Assign reserved IP

addresses to servers that require permanent IP settings.

Use the Router as a DHCP Server

By default, the router functions as a DHCP server, allowing it to assign IP, DNS server, and

default gateway addresses to all computers connected to the router’s LAN. The assigned

default gateway address is the LAN address of the router. The router assigns IP addresses to

the attached computers from a pool of addresses specified in this screen. Each pool address

is tested before it is assigned to avoid duplicate addresses on the LAN. For most

applications, the default DHCP and TCP/IP settings of the router are satisfactory.