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LTE TDD B2268H
User Guide
8 Network Address Translation (NAT)
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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LTE TDD B2268H
User Guide
8 Network Address Translation (NAT)
Issue 01 (2014-01-15)
Copyright © Huawei Technologies Co., Ltd.
70
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.
Page 78 / 155
LTE TDD B2268H
User Guide
8 Network Address Translation (NAT)
Issue 01 (2014-01-15)
Copyright © Huawei Technologies Co., Ltd.
71
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.
Page 79 / 155
LTE TDD B2268H
User Guide
8 Network Address Translation (NAT)
Issue 01 (2014-01-15)
Copyright © Huawei Technologies Co., Ltd.
72
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
Page 80 / 155
LTE TDD B2268H
User Guide
8 Network Address Translation (NAT)
Issue 01 (2014-01-15)
Copyright © Huawei Technologies Co., Ltd.
73
(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

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