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own queries. The proxy then takes the response from the external network and forwards it to the LAN client that pla-
ced the original query. In addition, the result from the query is stored for a defined time (configurable) to answer any
subsequent queries of the same type.
Dynamic DNS
Using Dynamic DNS you can also offer your own Internet services (e.g. WEB, FTP or e-mail servers). Usually you
must have a fixed line or a set IP address for this so that you can always be reached at the same URL (For example:
www.Funkwerk-ec.com).
You are assigned a new IP address by the ISP each time you dial in to the Internet however. Using Dynamic DNS you
can link this automatic (dynamic) IP address with a set name. The router will then inform your Dynamic DNS service
provider (e.g. www.dyndns.org) automatically of the new IP address. Internet enquiries for your Web services are
then automatically forwarded to your dynamic IP address via your service provider.
Using Dynamic DNS
·
Configure an Internet address (URL) at a Dynamic DNS service provider. For example, at
“www.dyndns.org” configure the address “www.my-homepage.dyndns.org”.
·
Configure the LAN client of the network in which you wish to offer your Web services with a set IP address.
For example, let’s say we want to configure a Web server with the IP address 192.168.1.200.
·
Activate the Dynamic DNS function in the router and enter the Internet address (URL) for your Dynamic
DNS provider (in the example here www.dyndns.org).
Add the necessary filters in the firewall to allow the PC with the Web services to be reached from an external
location.
- Configure port mapping for Port 80 (HTTP protocol) to IP address 192.168.1.200.
- Configure the filters that permit incoming and outgoing WAN connections at Port 80.
·
The router will automatically inform your Dynamic DNS provider of your current dynamic IP address each
time a connection is set up with the Internet. The information about the IP address is transferred after set-
ting up a new Internet connection, as well as during an ongoing Internet connection.
·
A PC in the Internet enters the address (URL) “www.my-homepage.dyndns.org”. In this way it reaches
your Dynamic DNS service provider. Your service provider reroutes the connection to your current
dynamic IP address.
·
Any incoming connection is handled in accordance with the configured filters. In the example given here
the incoming WAN connection at port 80 is forwarded to the LAN client with the IP address 192.168.1.200.
The available Internet sites of your Web server are displayed on the external PC.
NAT
NAT (Network Adress Translation) protects the connected LAN-clients against attacks from the Internet. Here, the
internal IP addresses are not passed on to the Internet. The router carries out the transfer to the Internet and distribu-
tes the incoming data packets in the internal system. This only requires one external IP address. The internal IP ad-
dresses are protected from attacks from outside. The internal IP addresses can not be targeted by hackers, as these IP
addresses are non-accessible.
Packet Filter Firewall
The integrated filter firewall packet also provides you with enhanced security against attacks from the Internet. A fi-
rewall acts as a logical wall for data packets between the Internet and the LAN which has »holes« for certain packets
(firewall rules, also known as filters), allowing these packets to pass through the wall. The filters are described by ru-
les whose configuration requires expert knowledge about the TCP/IP protocol family. The firewall of your PABX sys-
tem can be easily configured using a Filter Wizard in which you need to indicate (in plain text) whether you wish to
allow defined applications access to the Internet.
Introduction Router functions
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