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ZyXEL – SBG Support Notes
network is congested. This can cause a reduction in network performance
and make the network unfit for time critical applications such as
video-on-demand.
What is a Virtual Private Network (VPN)?
VPN stands for ‗Virtual Private Network'. In the past, when we needed to
transmit data in a secure way, we would need to have a site-to-site leased
line between the sites. This incurred very high costs for installing the lines.
A VPN gives users a secure way to access corporate network resources
over the Internet or other public or private networks without the expense
of leasing site-to-site lines.
A secure VPN is a combination of tunneling, encryption, authentication,
access control and auditing technologies/services used to transport traffic
over the Internet or any insecure network that uses the TCP/IP protocol
suite for communication.
L2TP/IPSec VPN Overview
The Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol used to
support virtual private networks (VPNs). However, it does not provide any
encryption or confidentiality by itself; it relies on an encryption protocol
that it passes within the tunnel to provide privacy. For this reason, L2TP is
often implemented along with IPSec. This is referred to as L2TP/IPSec.
IPSec VPN tunnel is established first and then an L2TP tunnel is built inside
it. When the process is complete, L2TP packets between the endpoints are
encapsulated by IPSec.
Since the L2TP packets themselves are wrapped and hidden within the
IPSec packets, no information about the internal private network can be
garnered from the encrypted packets. Also, it is not necessary to open UDP
port 1701 (used for L2TP) on firewalls between the endpoints, since the
inner packets are not acted upon until after IPSec data has been decrypted
and stripped, which only takes place at the endpoints.
PPTP VPN Overview
The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing
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