SatLink VSAT User Guide
Publication no. 101557
Copyright © 2009 – STM Group, Inc.
Page 59 (160)
10. Network Address Translation (NAT)
Network Address Translation is a mechanism to provide transparent IP-level access to the Internet from a
local site with a private address range without requiring all the hosts on the site to have globally valid IP
addresses. NAT translates addresses in incoming and outgoing IP packets by replacing the source address
in each outgoing IP packet with the globally valid IP address, and replacing the destination address in
each incoming IP packet with the private address of the destination host on the local site.
Network Address Port Translation (NAPT), sometimes called Port-Mapped NAT, is a popular variant of
NAT providing concurrency by translating TCP or UDP protocol port numbers as well as addresses.
The STM SatLink VSAT supports:
- Dynamic NAPT
- Static NAPT
- Static NAT.
To enable Network Address Translation (NAPT or static NAT) in the STM SatLink VSAT, use the web-
interface or the CLI command
ip nat enable. To show the status of the Network Address Port
Translation in the STM SatLink VSAT, use the web-interface or the CLI command
ip nat show:
4
If the user has enabled NAT in the STM SatLink VSAT then it is mandatory to set one global IP address
for NAT i.e. NAT IP address. The CLI command # ip nat global add <gladdr> is used to configure the
default global address. The following example shows how to configure a global IP address for NAT:-
Example:
# ip nat global add 10.10.1.10
After setting up the global IP address for the NAT, check the NAT
configuration by using the CLI command ip nat show
# ip nat show
NAT Configuration
-----------------
Network Address Port Translation (NAPT): Enabled
Global Address Table
If IP Address
dvb0 10.10.1.10
NAT Status
----------
Total Sessions 0
Active Sessions 0
Failed Sessions 0
Packet Translations 0
Example
# ip nat show
NAT:
----
Network Address Port Translation (NAPT): Enabled
NAT Status
-------------------
4
Please note that the CLI command # ip nat enable applies both for static NAT and NAPT even
though the
# ip nat show status output only mentions NAPT enabled.
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