CCNA 3 v7 Modules 6 – 8: WAN Concepts Test Online

Hint

There are four types of addresses in NAT terminology. Inside local address Inside global address Outside local address Outside global address The inside global address of PC1 is the address that the ISP sees as the source address of packets, which in this example is the IP address on the serial interface of R1, 209.165.200.224.

Hint

The NAT configuration on R1 is static NAT which translates a single inside IP address, 192.168.0.10 into a single public IP address, 209.165.200.255. If more hosts need translation, then a NAT pool of inside global address or overloading should be configured.

Hint

The show ip nat statistics, show ip nat translations, and debug ip nat commands are useful in determining if NAT is working and and also useful in troubleshooting problems that are associated with NAT. NAT is working, as shown by the hits and misses count. Because there are four misses, a problem might be evident. The standard access list numbered 1 is being used and the translation pool is named NAT as evidenced by the last line of the output. Both static NAT and NAT overload are used as seen in the Total translations line.

Hint

Because the packet is between RT2 and the web server, the source IP address is the inside global address of PC, 209.165.200.245.

Hint

The output shows that there are two inside global addresses that are the same but that have different port numbers. The only time port numbers are displayed is when PAT is being used. The same output would be indicative of PAT that uses an address pool. PAT with an address pool is appropriate when more than 4,000 simultaneous translations are needed by the company.

Hint

From the perspective of users behind NAT, inside global addresses are used by external users to reach internal hosts. Inside local addresses are the addresses assigned to internal hosts. Outside global addresses are the addresses of destinations on the external network. Outside local addresses are the actual private addresses of destination hosts behind other NAT devices.

Hint

Static NAT is a one-to-one mapping between an inside local address and an inside global address. By using static NAT, external devices can initiate connections to internal devices by using the inside global addresses. The NAT devices will translate the inside global address to the inside local address of the target host.

Hint

Dynamic NAT uses a pool of inside global addresses that are assigned to outgoing sessions. If there are more internal hosts than public addresses in the pool, then an administrator can enable port address translation with the addition of the overload keyword. With port address translation, many internal hosts can share a single inside global address because the NAT device will track the individual sessions by Layer 4 port number.

Hint

The source address for packets forwarded by the router to the Internet will be the inside global address of 209.165.200.225. This is the address that the internal addresses from the 10.6.15.0 network will be translated to by NAT.

Hint

There is not enough information given because the router might not be attached to the network yet, the interfaces might not have IP addresses assigned yet, or the command could have been issued in the middle of the night. The output does match the given configuration, so no typographical errors were made when the NAT commands were entered.

Hint

When two offices across a city are communicating , it is most likely that the data transmissions are over some type of WAN connection. Data communications within a campus are typically over LAN connections.

Hint

Private WAN technologies include leased lines, dialup, ISDN, Frame Relay, ATM, Ethernet WAN (an example is MetroE), MPLS, and VSAT.

Hint

When traveling employees need to connect to a corporate email server through a WAN connection, the VPN will create a secure tunnel between an employee laptop and the corporate network over the WAN connection. Obtaining dynamic IP addresses through DHCP is a function of LAN communication. Sharing files among separate buildings on a corporate campus is accomplished through the LAN infrastructure. A DMZ is a protected network inside the corporate LAN infrastructure.

Hint

The IPsec framework uses various protocols and algorithms to provide data confidentiality, data integrity, authentication, and secure key exchange. Two popular algorithms used to ensure that data is not intercepted and modified (data integrity and authenticity) are MD5 and SHA.

Hint

The IPsec framework uses various protocols and algorithms to provide data confidentiality, data integrity, authentication, and secure key exchange. Two algorithms that can be used within an IPsec policy to protect interesting traffic are AES, which is an encryption protocol, and SHA, which is a hashing algorithm.

Hint

When a web browser is used to securely access the corporate network, the browser must use a secure version of HTTP to provide SSL encryption. A VPN client is not required to be installed on the remote host, so a clientless SSL connection is used.

Hint

Integrity is a function of IPsec and ensures data arrives unchanged at the destination through the use of a hash algorithm. Confidentiality is a function of IPsec and utilizes encryption to protect data transfers with a key. Authentication is a function of IPsec and provides specific access to users and devices with valid authentication factors. Secure key exchange is a function of IPsec and allows two peers to maintain their private key confidentiality while sharing their public key.

Hint

Enterprise managed VPNs can be deployed in two configurations:

• Remote Access VPN – This VPN is created dynamically when required to establish a secure connection between a client and a VPN server. Remote access VPNs include client-based IPsec VPNs and clientless SSL VPNs.
• Site-to-site VPN – This VPN is created when interconnecting devices are preconfigured with information to establish a secure tunnel. VPN traffic is encrypted only between the interconnecting devices, and internal hosts have no knowledge that a VPN is used. Site-to-site VPNs include IPsec, GRE over IPsec, Cisco Dynamic Multipoint (DMVPN), and IPsec Virtual Tunnel Interface (VTI) VPNs.

Hint

Site-to-site VPNs are static and are used to connect entire networks. Hosts have no knowledge of the VPN and send TCP/IP traffic to VPN gateways. The VPN gateway is responsible for encapsulating the traffic and forwarding it through the VPN tunnel to a peer gateway at the other end which decapsulates the traffic.

Hint

The IPsec framework uses various protocols and algorithms to provide data confidentiality, data integrity, authentication, and secure key exchange. DH (Diffie-Hellman) is an algorithm used for key exchange. DH is a public key exchange method that allows two IPsec peers to establish a shared secret key over an insecure channel.

Hint

NAT overloading, also known as Port Address Translation (PAT), uses port numbers to differentiate between multiple internal hosts.

Hint

In static NAT a single inside local address, in this case 192.168.0.10, will be mapped to a single inside global address, in this case 209.165.200.225. Internet hosts will send packets to PC1 and use as a destination address the inside global address 209.165.200.225.

Hint

Because no outside local or outside global address is referenced, the traffic from a source IPv4 address of 192.168.254.253 is being translated to 192.0.2.88 by using static NAT. In the output from the command show ip nat translations, the inside local IP address of 192.168.2.20 is being translated into an outside IP address of 192.0.2.254 so that the traffic can cross the public network. A public IPv4 device can connect to the private IPv4 device 192.168.254.253 by targeting the destination IPv4 address of 192.0.2.88.

Hint

Private WANs can use T1/E1, T3/E3, PSTN, ISDN, Metro Ethernet, MPLS, Frame Relay, ATM, or VSAT technology.

Hint

Although LANs and WANs can employ the same network media and intermediary devices, they serve very different areas and purposes. The administrative and geographical scope of a WAN is larger than that of a LAN. Bandwidth speeds are slower on WANs because of their increased complexity. The Internet is a network of networks, which can function under either public or private management.

Hint

A site-to-site VPN is created between the network devices of two separate networks. The VPN is static and stays established. The internal hosts of the two networks have no knowledge of the VPN.

Hint

Packets in a VPN are encapsulated with the headers from one or more VPN protocols before being sent across the third party network. This is referred to as “tunneling”. These outer headers can be used to route the packets, authenticate the source, and prevent unauthorized users from reading the contents of the packets.

Hint

A VPN is a private network that is created over a public network. Instead of using dedicated physical connections, a VPN uses virtual connections routed through a public network between two network devices.

Hint

The output of show ip nat statistics shows that the inside interface is FastEthernet0/0 but that no interface has been designated as the outside interface. This can be fixed by adding the command ip nat outside to interface Serial0/0/0.

Hint

In order for NAT translations to work properly, both an inside and outside interface must be configured for NAT translation on the router.

Hint

From the perspective of a NAT device, inside global addresses are used by external users to reach internal hosts. Inside local addresses are the addresses assigned to internal hosts. Outside global addresses are the addresses of destinations on the external network. Outside local addresses are the actual private addresses of destination hosts behind other NAT devices.

Hint

The output displayed in the exhibit is the result of the show ip nat translations command. Static NAT entries are always present in the NAT table, while dynamic entries will eventually time out.

Hint

WANs cover a greater geographic area than LANs do, so having employees distributed across many locations would require the implementation of WAN technologies to connect those locations. Customers will access corporate web services via a public WAN that is implemented by a service provider, not by the enterprise itself. When employee numbers grow, the LAN has to expand as well. A WAN is not required unless the employees are in remote locations. LAN security is not related to the decision to implement a WAN.

Hint

The IPsec framework uses various protocols and algorithms to provide data confidentiality, data integrity, authentication, and secure key exchange. The Hashed Message Authentication Code (HMAC) is a data integrity algorithm that uses a hash value to guarantee the integrity of a message.

Hint

The IPsec framework uses various protocols and algorithms to provide data confidentiality, data integrity, authentication, and secure key exchange. Two popular algorithms that are used to ensure that data is not intercepted and modified (data integrity) are MD5 and SHA. AES is an encryption protocol and provides data confidentiality. DH (Diffie-Hellman) is an algorithm that is used for key exchange. RSA is an algorithm that is used for authentication.

Hint

VPNs can be managed and deployed as either of two types:

• Enterprise VPNs – Enterprise-managed VPNs are a common solution for securing enterprise traffic across the internet. Site-to-site and remote access VPNs are examples of enterprise managed VPNs.
• Service Provider VPNs – Service provider managed VPNs are created and managed over the provider network. Layer 2 and Layer 3 MPLS are examples of service provider managed VPNs. Other legacy WAN solutions include Frame Relay and ATM VPNs.

Hint

Because no outside local or outside global address is referenced, the traffic from a source IPv4 address of 192.168.254.253 is being translated to 192.0.2.88 by using static NAT. In the output from the command show ip nat translations, the inside local IP address of 192.168.2.20 is being translated into an outside IP address of 192.0.2.254 so that the traffic can cross the public network. A public IPv4 device can connect to the private IPv4 device 192.168.254.253 by targeting the destination IPv4 address of 192.0.2.88.

Hint

Because no outside local or outside global address is referenced, the traffic from a source IPv4 address of 192.168.254.253 is being translated to 192.0.2.88 by using static NAT. In the output from the command show ip nat translations, the inside local IP address of 192.168.2.20 is being translated into an outside IP address of 192.0.2.254 so that the traffic can cross the public network. A public IPv4 device can connect to the private IPv4 device 192.168.254.253 by targeting the destination IPv4 address of 192.0.2.88.