3Com 3CRWER300-73 Router Manual PDF (Setup & Configuration Guide)

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Internet Settings

79

DNS

Domain Name Service (or Server) is an Internet service that translates

domain names into IP addresses. Because domain names are alphabetic,

they're easier to remember. The Internet however, is really based on IP

addresses. Every time you use a domain name, a DNS service must

translate the name into the corresponding IP address. For example, the

domain name www.example.com might translate to 198.105.232.4.

Figure 61

DNS Screen

If the DNS information is automatically provided by your ISP every time

you connect to it, check the

Automatic from ISP

checkbox.

If your ISP provided you with specific DNS addresses to use, enter them

into the appropriate fields on this screen and click

Apply

.

Many ISPs do not require you to enter this information into the Router. If

you are using a Static IP connection type, you may need to enter a

specific DNS address and secondary DNS address for your connection to

work properly. If your connection type is Dynamic or PPPoE, it is likely that

you do not have to enter a DNS address.

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80

C

HAPTER

5: C

ONFIGURING

THE

R

OUTER

Clone MAC address

To configure the Hostname and Clone MAC Address information for your

Router, select

Internet Settings

, then go to the

Clone MAC address

tab.

Figure 62

Hostname and Clone MAC Address Screen

1

Some ISPs require a host name. If your ISP has this requirement, enter the

host name in the

Host Name

field.

2

Three different ways to configure the WAN MAC Address:

■

If your ISP requires an assigned MAC address, enter the values in the

WAN

MAC address

field.

or

■

If the computer that you are using is the one that was previously

connected directly to the cable modem, click

Clon

e.

or

■

To reset the MAC Address to the default, click

Reset MAC

.

3

Click

Apply

to save the settings.

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Firewall

81

Firewall

This section is for configuration settings of the Router’s firewall function.

Your Router is equipped with a firewall that will protect your network

from a wide array of common hacker attacks including Ping of Death

(PoD) and Denial of Service (DoS) attacks. You can turn the firewall

function off if needed. Turning off the firewall protection will not leave

your network completely vulnerable to hacker attacks, but 3Com

recommends that you leave the firewall enabled whenever possible.

SPI

Stateful Packet Inspection (SPI) - The Intrusion Detection Feature of the

Router limits access for incoming traffic at the WAN port.

This feature is called a "stateful" packet inspection, because it examines

the contents of the packet to determine the state of the communications;

i.e., it ensures that the stated destination computer has previously

requested the current communication. This is a way of ensuring that all

communications are initiated by the recipient computer and are taking

place only with sources that are known and trusted from previous

interactions. In addition to being more rigorous in their inspection of

packets, stateful inspection firewalls also close off ports until connection

to the specific port is requested.

Figure 63

Firewall Screen

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82

C

HAPTER

5: C

ONFIGURING

THE

R

OUTER

To enable the firewall function:

1

Select the level of protection (High, Medium, or Low) that you desire from

the

Firewall level

drop-down menu.

2

Click

Apply

.

■

For low and medium levels of firewall protection, refer to

Figure 64

.

For low level of firewall protection, the DoS and SPI functions are both

off. For medium level of firewall protection, DoS in on, but SPI is off.

■

For high level of firewall protection, refer to

Figure 65

. Both DoS and

SPI are on for this level of firewall protection. The higher the firewall

level is, the safer that your network is.

Figure 64

Low and Medium Level Firewall Protection Screen

When abnormal network activity occurs, an alerting email will be sent out

to you. Enter the following information to receive the email:

■

Your E-mail Address

■

SMTP Server Address

■

User name

■

Password

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Firewall

83

Figure 65

High Level Firewall Protection Screen

If you select high level of protection, you would have an option to

configure additional parameters for the firewall.

■

Fragmentation half-open wait - Configures the number of seconds

that a packet state structure remains active. When the timeout value

expires, the Router drops the un-assembled packet, freeing that

structure for use by another packet.

■

TCP SYN wait - Defines how long the software will wait for a TCP

session to synchronize before dropping the session.

■

TCP FIN wait - Specifies how long a TCP session will be maintained

after the firewall detects a FIN packet.

■

TCP connection idle timeout - The length of time for which a TCP

session will be managed if there is no activity.

■

UDP session idle timeout - The length of time for which a UDP session

will be managed if there is no activity.

■

H.323 data channel idle timeout - The length of time for which an

H.323 session will be managed if there is no activity.

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