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N600 Wireless Dual Band Gigabit Router WNDR3700v4

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.



To view or change the WAN settings:

Select

Advanced > Setup > WAN Setup

The following settings are available:

•

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 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 setting 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

. The IGPM Proxying feature lets a LAN computer receive the

multicast traffic directed to it from the Internet. Selecting this check box prevents this from

occurring.

•

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. You should change the setting in this

field only if you are sure that it is necessary for your ISP connection. See

Change the

MTU Size

on page

38.

•

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

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N600 Wireless Dual Band Gigabit Router WNDR3700v4

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.

•

Disable SIP ALG

. The Session Initiation Protocol (SIP) Application Level Gateway (ALG)

is enabled by default to optimize VoIP phone calls that use the SIP. The Disable SIP ALG

check box allows you to disable the SIP ALG. Disabling the SIP ALG might be useful

when running certain applications.

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 recognizes some of these applications and works correctly with them, but

other applications 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.

The router usually detects and discards incoming traffic from the Internet that is not a

response to local computers or a service that you set up in the Port Forwarding/Port

Triggering screen. Instead of discarding this traffic, you can have the router forward the traffic

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



To set up a default DMZ server:

1.

On the WAN Setup screen, select the

Default DMZ Server

check box.

2.

Type the IP address.

3.

Click

Apply

.

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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 a device in the data path has a lower MTU

setting than the other devices, the data packets are split or “fragmented” to accommodate the

device with the smallest MTU.

The best MTU setting for NETGEAR equipment is often just the default value. In some

situations, changing the value fixes one problem but causes another. Leave the 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 does not open, or displays only part of a web page

-

Yahoo email

-

MSN portal

-

America Online’s DSL service

•

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. For example, you might not be able to access certain

websites, frames within websites, 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 1.

Common MTU sizes

MTU

Application

1500

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

connections that do not use PPPoE or VPN, 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.

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

To change the MTU size:

1.

Select

Advanced > Setup > WAN Setup

.

2.

In the MTU Size field, enter a value from 64 to 1500.

3.

Click

Apply

to save the settings.

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 are suitable for most applications. If your network requires a different IP addressing

scheme, you can change these settings in the LAN Setup screen.



To change the LAN settings:

Note:

If you change the LAN IP address of the router, you are

disconnected. To use the router menus, you must use a browser to

connect to the new IP address and log in again.

1460

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

1436

Used in PPTP environments or with VPN.

1400

Maximum size for AOL DSL.

576

Typical value to connect to dial up ISPs.

Table 1.

Common MTU sizes

(Continued)

MTU

Application

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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.

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

addresses 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 setting 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.