3Com 3C16111 - SuperStack 3 Firewall Web Site Filter, User Manual

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ETWORKING
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ONCEPTS
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Linking two or more Private Networks Together
VPN is the perfect way to connect branch offices and business
partners to the primary business. Using VPN over the Internet, instead
of leased site-site lines, offers significant cost savings and improved
performance.
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Using the IRE VPN Client for Secure Remote Management
Using the included IRE VPN client for Windows, a secure, encrypted
tunnel may be created that allows the administrator to remotely
manage the Firewall over the Internet.
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Accessing Machines Using Private Addressing behind NAT
When NAT (Network Address Translation) is enabled, remote users are
not able to access hosts on the LAN unless the host is designated a
Public LAN Server for that specific protocol. Since the VPN Tunnel
terminates inside the LAN, remote users will be able to access all
computers that use private IP addresses on the LAN.
Basic VPN Terms and
Concepts
The following explains the most common terms and expressions used in
VPN
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VPN Tunnel
Tunnelling is the encapsulation of point-point transmission inside IP
packets. A VPN Tunnel is a term that is used to describe a connection
between two or more private nodes or LANs over a public network,
typically the Internet. Encryption is often used to maintain the
confidentiality of private data when travelling over the Internet.
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Encryption
Encryption is a mathematical operation that transforms data from
“clear text” (something that a human or a program can interpret) to
“cipher text” (something that cannot be interpreted). Usually the
mathematical operation requires that an alphanumeric “key” be
supplied along with the clear text. The key and clear text are
processed by the encryption operation which leads to the data
scrambling that makes encryption secure. Decryption is the opposite
of encryption: it is the mathematical operation that transforms cipher
text to clear text. Decryption also requires a key.
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Key
A key is an alphanumeric string that is used by the encryption
operation to transform clear text into cipher text. Keys used in VPN
DUA1611-0AAA02.book Page 186 Thursday, August 2, 2001 4:01 PM