Product specifications

Chapter 6: Connection Management Efficient Networks
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Router family
Command Line Interface Guide
Page 6-46 Efficient Networks
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Flags ............... 1
To close a PPPoE session before it terminates, use the pppoe close command. The
session is specified by its number. (Use the PPPoE/n number from the ifs output or
the PPPoE/Ifs number from the pppoe list output.)
VPN
VPN (Virtual Private Network) is a term used to describe the connection between two
or more private (or trusted) networks when the connection is carried across a public
(non-trusted) network. A VPN will isolate the private traffic while it is on the public
network so that the connection seems private.
A VPN can be created in many ways using many different technologies. In this
section, we will briefly discuss the difference between physical (Layer-1), transport
(Layer-2), and network (Layer-3) methods of creating a private network. Then we will
discuss the protocols and equipment standards of a Layer-3 VPN.
Physical (Layer-1) VPNs
ISDN, analog dial-up
Most of us don’t think of dial-up services as VPNs, but they have many of the same
characteristics. For example, analog dial-up allows a user to connect to a private
network (Corporate LAN) by using a public network (PSTN) as the transport.
Advantages
Accessible: The biggest advantage of using the PSTN is that the network reaches
almost every location on the planet. Almost anyone can place a phone call to his/her
data center because there are telephones all over the world. The network is
established and accessible.
Connect to multiple sites: Using the PSTN allows a person to connect to multiple
locations by simply dialing different phone numbers. It is very flexible.
Disadvantages
Long distance charges: If the locations being dialed are not local, then connection
costs can get very expensive and run up a large bill quickly.
Data throughput limitations: The data throughput using the PSTN has limits due to the
technology that is used to pass traffic. If high bandwidth is required, then analog or
ISDN dial-up is not an option.