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User Guide

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Issue 01 (2014-01-15)

Copyright © Huawei Technologies Co., Ltd.

69

Figure 8-3

Port Forwarding: Add/Edit

The following table describes the labels in this screen.

Table 8-2

Port Forwarding: Add/Edit

LABEL

DESCRIPTION

Service Name

Enter a name to identify this rule using keyboard characters (A-Z, a-z,

1-2 and so on).

WAN Interface

This is the WAN interface through which the service is forwarded.

Start Port

Enter the original destination port for the packets.

To forward only one port, enter the port number again in the

External

End Port field.

To forward a series of ports, enter the start port number here and the end

port number in the

External End Port

field.

End Port

Enter the last port of the original destination port range.

To forward only one port, enter the port number in the

External Start

Port

field above and then enter it again in this field.

To forward a series of ports, enter the last port number in a series that

begins with the port number in the

External Start Port

field above.

Translation Start

Port

This shows the port number to which you want the LTE Device to

translate the incoming port. For a range of ports, enter the first number

of the range to which you want the incoming ports translated.

Translation End

Port

This shows the last port of the translated port range.

Server IP Address

Enter the inside IP address of the virtual server here.

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User Guide

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LABEL

DESCRIPTION

Protocol

Select the protocol supported by this virtual server. Choices are

TCP

,

UDP

, or

TCP/UDP

.

Apply

Click

Apply

to save your changes.

Back

Click

Back

to return to the previous screen without saving.

8.3 The DMZ Screen

Use this page to set the IP address of your network DMZ (if you have one) for the LTE Device.

All incoming packets received by this LTE Device's WAN interface will be forwarded to the

default server you set.

Click

Network Setting > NAT > DMZ

to display the following screen.

The configuration you set in this screen takes priority than the

Network Setting > NAT > Port

Forwarding

screen.

Figure 8-4

Network Setting > NAT > DMZ

The following table describes the fields in this screen.

Table 8-3

Network Setting > NAT > DMZ

LABEL

DESCRIPTION

Default Server

Address

Enter the IP address of your network DMZ host, if you have one.

0.0.0.0

means this feature is disabled.

Apply

Click

Apply

to save your changes.

Cancel

Click

Cancel

to restore your previously saved settings.

8.4 The Sessions Screen

Use the

Sessions

screen to limit the number of concurrent NAT sessions each client can use.

Click

Network Setting > NAT > Sessions

to display the following screen.

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User Guide

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Issue 01 (2014-01-15)

Copyright © Huawei Technologies Co., Ltd.

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Figure 9-5

Network Setting > NAT > Sessions

The following table describes the fields in this screen.

Table 8-4

Network Setting > NAT > Sessions

LABEL

DESCRIPTION

MAX

NAT

Session

Use this field to set a common limit to the number of concurrent NAT sessions

each client computer can have.

If only a few clients use peer to peer applications, you can raise this number to

improve their performance. With heavy peer to peer application use, lower this

number to ensure no single client uses too many of the available NAT sessions.

Apply

Click

Apply

to save your changes.

Cancel

Click

Cancel

to restore your previously saved settings.

8.5 The ALG Screen

Use the

ALG

screen to enable or disable SIP Application Layer Gateway (ALG) on the LTE

Device. Click

Apply

to save your change.

The SIP ALG allows SIP calls to pass through NAT by examining and translating IP addresses

embedded in the data stream. When the LTE Device registers with the SIP register server, the

SIP ALG translates the LTE Device's private IP address inside the SIP data stream to a public IP

address. You do not need to use STUN or an outbound proxy if you enable the SIP ALG.

For the LTE environment, the LTE interface may experience heavy overhead when sending SIP

re-registration requests due to SIP server NAT session timeout. This default NAT session

timeout value (3600 seconds) helps to decrease the chance of this happening.

Figure 8-5

Network Setting > NAT > ALG

8.6 Technical Reference

This section provides some technical background information about the topics covered in this

chapter.

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User Guide

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Issue 01 (2014-01-15)

Copyright © Huawei Technologies Co., Ltd.

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8.6.1 NAT Definitions

Inside/outside denotes where a host is located relative to the LTE Device, for example, the

computers of your subscribers are the inside hosts, while the web servers on the Internet are the

outside hosts.

Global/local denotes the IP address of a host in a packet as the packet traverses a router, for

example, the local address refers to the IP address of a host when the packet is in the local

network, while the global address refers to the IP address of the host when the same packet is

traveling in the WAN side.

Note that inside/outside refers to the location of a host, while global/local refers to the IP

address of a host used in a packet. Thus, an inside local address (ILA) is the IP address of an

inside host in a packet when the packet is still in the local network, while an inside global

address (IGA) is the IP address of the same inside host when the packet is on the WAN side. The

following table summarizes this information.

Table 8-5

NAT Definitions

ITEM

DESCRIPTION

Inside

This refers to the host on the LAN.

Outside

This refers to the host on the WAN.

Local

This refers to the packet address (source or destination) as the packet travels on

the LAN.

Global

This refers to the packet address (source or destination) as the packet travels on

the WAN.

NAT never changes the IP address (either local or global) of an outside host.

8.6.2 What NAT Does

In the simplest form, NAT changes the source IP address in a packet received from a subscriber

(the inside local address) to another (the inside global address) before forwarding the packet to

the WAN side. When the response comes back, NAT translates the destination address (the

inside global address) back to the inside local address before forwarding it to the original inside

host. Note that the IP address (either local or global) of an outside host is never changed.

The global IP addresses for the inside hosts can be either static or dynamically assigned by the

ISP. In addition, you can designate servers, for example, a web server and a Telnet server, on

your local network and make them accessible to the outside world. If you do not define any

servers, NAT offers the additional benefit of firewall protection. With no servers defined, your

LTE Device filters out all incoming inquiries, thus preventing intruders from probing your

network. For more information on IP address translation, refer to

RFC 1631

,

The IP Network

Address Translator (NAT)

.

8.6.3 How NAT Works[h1]

Each packet has two addresses-a source address and a destination address. For outgoing packets,

the ILA (Inside Local Address) is the source address on the LAN, and the IGA (Inside Global

Address) is the source address on the WAN. For incoming packets, the ILA is the destination

address on the LAN, and the IGA is the destination address on the WAN. NAT maps private

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(local) IP addresses to globally unique ones required for communication with hosts on other

networks. It replaces the original IP source address (and TCP or UDP source port numbers for

Many-to-One and Many-to-Many Overload NAT mapping) in each packet and then forwards it

to the Internet. The LTE Device keeps track of the original addresses and port numbers so

incoming reply packets can have their original values restored. The following figure illustrates

this.

Figure 8-6

How NAT Works