Chapter 3: Advanced Configuration

34

Chapter 3

Network Web Page Group

WAN Web Page (Fig. 22)

This page gives you the ability to enter some data your cable company may require, as explained

before in Mandatory User Configuration. In addition, it enables you to view your WAN side IP

address and lease information.

Your gateway can provide NAT/PAT (Network and Port Address Translation) as an element of

security to prevent others from reaching your PCs when not authorized. To accomplish this, the

gateway watches packets you send from your PC to Internet sites. Each time you send to a site

(destination IP address) and application at that site (port), it translates your PC’s original IP and

source port to new ones, and adds a row to its Connection Table maintained internally. (Note the

different meaning of ‘connection’ here to describe an IP connection versus a physical cabling

connection). If and when that site/application replies, it looks up the connection and reverses the

IP/port process to direct the response to your PC.

The Connection Table manages itself, but you can also force this table to be cleared manually. To

do this, click the

Renew NAT Lease

button.

You can enter a spoofed MAC address that causes your gateway networking stack to use that

MAC address when communicating instead of the usual WAN MAC address (CM label + 2, as

explained in Chapter 2). Enter the desired MAC address and click

Apply

.

Caution: If you enter a MAC address in use by another party, it can cause an address conflict on

the network that could affect both you and that party.

Fig. 22

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Chapter 3

35

LAN and Computers Web Pages (Fig. 23 and 24)

These pages give you the ability to activate and deactivate the DHCP server function of your

gateway, and, if the DHCP server is activated, to see DHCP leases it has provided.

With this function activated, your cable company’s DHCP server provides one IP address for your

gateway, and your gateway’s DHCP server provides IP addresses, starting at the address you set in

IP Address on the LAN page

, to your PCs. A DHCP server

leases

an IP address with an expiration

time.

To change the lowest IP address that your gateway will issue to your PCs, enter it into the

IP

Address

box and then click

Apply

.

To set the maximum number of PCs to which the gateway will issue IP addresses, enter it in the

Number of CPEs

box and then click

Apply

. (

CPE

is another term sometimes used for PC.)

The

Computers web page

section shows leases the gateway DHCP server has made, including the

IP and MAC addresses of each PC’s TCP/IP stack. Since MAC addresses are unique and permanently

fixed into hardware, you can identify any PC listed by its MAC address. The gateway provides

leases for 7 days, and has an automatic renewal mechanism that will keep extending a lease as

long as the associated PC remains active. If your PC is set to “obtain an IP address automatically,”

it is set to perform DHCP each time it is rebooted.

You can cancel an IP address lease by selecting it in the

DHCP Client Lease Info

list and then

clicking the

Force Available

button. If you do this, you may have to perform a DHCP Renew on

that PC, so it can obtain a new lease.

Fig. 23

Fig. 24

Chapter 3: Advanced Configuration

36

Chapter 3

Advanced Web Page Group

Options Web Page (Fig. 25)

This page allows you to enable/disable some features of the Wireless Cable Gateway. Check

WAN

Blocking

and then click

Apply

to prevent others on the WAN side from being able to ping your

gateway. With WAN Blocking on, your gateway will not respond to pings it receives, effectively

“hiding” your gateway.

Check

Ipsec Pass Through

and then click

Apply

to enable IpSec type packets to pass WAN <=>

LAN. IpSec (IP Security)

is a security mechanism used in Virtual Private Networks (VPNs). E.g., your

employer may offer VPN connectivity to your office network to provide security.

Check

PPTP Pass Through

and then click

Apply

to enable PPTP type packets to pass WAN <=>

LAN. PPTP (Point to Point Tunneling Protocol) is another mechanism sometimes used in VPNs.

Check

Remote Config Management

and then click

Apply

to make the configuration web pages

in your gateway accessible from the WAN side. Then you could, for example, access your home

gateway configuration from your workplace, if that location also had Internet connectivity.

Page access is limited to only those who know the gateway access password you set using the

Status...Password web page.

This function works only if your gateway is in the RG mode. When accessing your gateway from

a remote location, you must use HTTP port 8080 and your IP Stack 3 address. This is the "WAN IP

address" that appears at the Network...WAN page. For example, if this IP address were 157.254.5.7,

you would navigate to http://157.254.5.7:8080 to reach your gateway from a remote location.

Fig. 25

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Chapter 3

37

Check

Multicast Enable

and then click

Apply

to enable multicast traffic to pass WAN <=> LAN.

You may need to enable this to see some types of broadcast streaming and content on the

Internet, such as webcasting of a popular live event.

IP Filtering Web Page (Fig. 26)

This page enables you to enter the IP address ranges of PCs on your LAN that you don’t want to

have outbound access to the WAN. These PCs can still communicate with each other on your LAN,

but packets they originate to WAN addresses are blocked by the gateway.

MAC Filtering Web Page (Fig. 27)

This page enables you to enter the MAC address of specific PCs on your LAN that you wish to NOT

have outbound access to the WAN. As with IP filtering, these PCs can still communicate with each

other through the gateway, but packets they send to WAN addresses are blocked.

Fig. 26

Fig. 27

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38

Chapter 3

Fig. 28

Port Filtering Web Page (Fig. 28)

This page enables you to enter ranges of destination ports (applications) that you don’t want

your LAN PCs to send packets to. Any packets your LAN PCs send to these destination ports will

be blocked. For example, you could block access to worldwide web browsing (HTTP = port 80) but

still allow email service (SMTP port 25 and POP-3 port 110).

To enable filtering, set Start Port and

End Port for each range, and click Apply. To block only one port, set both Start and End ports the

same.