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Virtual Private Network (VPN)
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Why Virtual Private Network (VPN)?
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The General Idea: Using "Proxy"
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Proxy at the Transport LayerSSH Tunneling
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Proxy at the IP LayerIP Tunneling
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IP Tunneling: IPSec Approach
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IP Tunneling: SSL/TLS Approach
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Review: Tunneling
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Virtual Networking Technologies
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The TUN/TAP Interface
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Packet Tunneling
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How VPN Works: Outgoing Traffic
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Creating TUN/TAP Interface
Creating a TUN Interface
Show the TUN Interface
Set the IP Address for the TUN Interface
Bring Up the TUN Interface
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Network Configuration
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Read from the TUN Interface (ping 192.168.60.5)
Read From the TUN Interface
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Create a Packet
Write to the TUN Interface
Write to the TUN interface
# cat icmp.bin >& 3
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Question: Network Setup
Question: Where should we run the following commands?
A: $ sudo route add -net 10.4.2.0/24 gw 192.168.60.5 eth19
B: $ sudo route add -net 10.4.2.0/24 tun0
C: $ sudo route add -net 192.168.60.0/24 tun0
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Testing VPN
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Case Study: SURA (Syracuse University VPN)
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SURA: Before Running VPN
Interfaces
Routing table (Windows: Route PRINT)
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SURA: After Running VPN
Interfaces
Routing table
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Question: Find the IP Addresses
What is my computer’s real IP address (i.e., the IP address of my WiFi card)?1.
What is the IP address of the VPN server? 2.What is the IP address of my TUN interface? 3.
SU's VPN is called SURA. If you run SURA on your computer, once you have logged in, a VPN tunnel will be established between your host machine and SU's network (128.230.0.0/16). After I run SURA, the routing table on my computer appears as in the picture below. Please answer the following questions.
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Lab Setup
Manually set up the IP address for the "Internal Network" adaptor on VPN Server
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Creating a VPN Tunnel using TUN/TAP
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Packet Flow
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Encrypting the Tunnel
Packet Flow
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Bypassing Firewalls: Another Popular Use of VPN
Internet
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A Related Lab: Bypassing Firewalls using VPN
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