200-301.prepaway.premium.exam.160q

200-301.prepaway.premium.exam.160q.a. 172.16.1.0/24 path b. 172.16.2.0/24 path c. 8.888 path d. 9.999 path7.2 Fundamentals7.2.1 VPN Fundamentals Leased lines have excellent security; the router at one end can trust the identity of the device at the other end of the link. The router on the receiving end also has reason to be confident that an attacker cannot intercept data in transit or modify it to cause some damage. a VPN seeks to provide the same security features as a leased line while sending data over a network that is open to other networks, especially when the data often has to cross the Internet. Even when sending data over a public network like the Internet, VPNs can provide the following features. Confidentiality: Prevents anyone in the Internet (man-in-the-middle) from copying packets in the Internet and being able to read them. Authentication: Verifies that the VPN packet sender is a legitimate and unexploitable device for attackers.Data Integrity: Verifies that the packet has not been modified during transmission over the Internet. Anti-retransmission: Prevents a man-in-the-middle from copying a packet sent by a legitimate user and then resending the packet posing as a legitimate user. To achieve these goals, two devices at the edge of the Internet are required to build a VPN, sometimes called a VPN tunnel, which adds a header to the source packet that includes fields that allow the VPN device to perform all of the above functions. This means that even if a copy of the packet can be obtained during transmission over the Internet, the contents of the source packet cannot be deciphered.Figure 7-1 illustrates the general concept of a typical VPN tunnel. In this example, because the VPN connects two sites in a company, such a VPN is called a site-to-site VPN. This VPN is also called a site-to-site (Intranet) VPNO because the connected sites are internal to a single company.1.2 Foundation Content 143Figure 7-1 VPN Tunneling Concept for Site-to-Site IntranetVPN144 Chapter 7 Virtual Private NetworksThe following steps are shown in the figure, explaining and illustrating the entire information flow.Step 1 Host PC1 (10.2.2.2) on the right sends a packet to web server S1 (10.1.1.1), which is not yet using a VPN.