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A gateway is used to connect two networks using dissimilar protocols at the lower layers or it could also be at the highest level of the protocol stack.

Important Note:

For the purpose of the exam, you have to remember that a gateway is not synonymous to the term firewall.

The second thing you must remembers is the fact that a gateway act as a translation device.

It could be used to translate from IPX to TCP/IP for example. It could be used to convert different types of applications protocols and allow them to communicate together. A gateway could be at any of the OSI layers but usually tend to be higher up in the stack.

For your exam you should know the information below:

Repeaters

A repeater provides the simplest type of connectivity, because it only repeats electrical signals between cable segments, which enables it to extend a network. Repeaters work at the physical layer and are add-on devices for extending a network connection over a greater distance. The device amplifies signals because signals attenuate the farther they have to travel.

Repeaters can also work as line conditioners by actually cleaning up the signals. This works much better when amplifying digital signals than when amplifying analog signals, because digital signals are discrete units, which makes extraction of background noise from them much easier for the amplifier. If the device is amplifying analog signals, any accompanying noise often is amplified as well, which may further distort the signal.

A hub is a multi-port repeater. A hub is often referred to as a concentrator because it is the physical communication device that allows several computers and devices to communicate with each other. A hub does not understand or work with IP or MAC addresses. When one system sends a signal to go to another system connected to it, the signal is broadcast to all the ports, and thus to all the systems connected to the concentrator.

Repeater

Image Reference- http://www.erg.abdn.ac.uk/~gorry/course/images/repeater.gif

Bridges

A bridge is a LAN device used to connect LAN segments. It works at the data link layer and therefore works with MAC addresses. A repeater does not work with addresses; it just forwards all signals it receives. When a frame arrives at a bridge, the bridge determines whether or not the MAC address is on the local network segment. If the MAC address is not on the local network segment, the bridge forwards the frame to the necessary network segment.

Bridge

Image Reference- http://www.oreillynet.com/network/2001/01/30/graphics/bridge.jpg

Routers

Routers are layer 3, or network layer, devices that are used to connect similar or different networks. (For example, they can connect two Ethernet LANs or an Ethernet LAN to a Token Ring LAN.) A router is a device that has two or more interfaces and a routing table so it knows how to get packets to their destinations. It can filter traffic based on access control lists (ACLs), and it fragments packets when necessary. Because routers have more network-level knowledge, they can perform higher-level functions, such as calculating the shortest and most economical path between the sending and receiving hosts.

Router and Switch

Image Reference- http://www.computer-networking-success.com/images/router-switch.jpg

Switches

Switches combine the functionality of a repeater and the functionality of a bridge. A switch amplifies the electrical signal, like a repeater, and has the built-in circuitry and intelligence of a bridge. It is a multi-port connection device that provides connections for individual computers or other hubs and switches.

Gateways

Gateway is a general term for software running on a device that connects two different environments and that many times acts as a translator for them or somehow restricts their interactions. Usually a gateway is needed when one environment speaks a different language, meaning it uses a certain protocol that the other environment does not understand. The gateway can translate Internetwork Packet Exchange (IPX) protocol

packets to IP packets, accept mail from one type of mail server and format it so another type of mail server can accept and understand it, or connect and translate different data link technologies such as FDDI to Ethernet.

Gateway Server

Image Reference- http://static.howtoforge.com/images/screenshots/556af08d5e43aa768260f9e589dc547f-3024.jpg

The following answers are incorrect:

Repeater - A repeater provides the simplest type of connectivity, because it only repeats electrical signals between cable segments, which enables it to extend a network. Repeaters work at the physical layer and are add-on devices for extending a network connection over a greater distance. The device amplifies signals because signals attenuate the farther they have to travel.

Bridges - A bridge is a LAN device used to connect LAN segments. It works at the data link layer and therefore works with MAC addresses. A repeater does not work with addresses; it just forwards all signals it receives. When a frame arrives at a bridge, the bridge determines whether or not the MAC address is on the local network segment. If the MAC address is not on the local network segment, the bridge forwards the frame to the necessary network segment.

Routers - Routers are layer 3, or network layer, devices that are used to connect similar or different networks. (For example, they can connect two Ethernet LANs or an Ethernet LAN to a Token Ring LAN.) A router is a device that has two or more interfaces and a routing table so it knows how to get packets to their destinations. It can filter traffic based on access control lists (ACLs), and it fragments packets when necessary.

Following reference(s) were/was used to create this question:

CISA review manual 2014 Page number 263

Official ISC2 guide to CISSP CBK 3rd Edition Page number 229 and 230

The data link layer (layer 2) establishes the communications link between individual devices over a physical link or channel. It also ensures that messages are delivered to the proper device and translates the messages from layers above into bits for the physical layer (layer 1) to transmit.

Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 3: Telecommunications and Network Security (page 83).

Communications security and techniques are the best area for addressing this objective.

"Information security management and techniques" is incorrect. While the overall information security program would include this objective, communications security is the more specific and better answer.

"Client security management and techniques" is incorrect. While client security plays a part in this overall objective, communications security is the more specific and better answer.

"Server security management and techniques" is incorrect. While server security plays a part in this overall objective, communications security is the more specific and better answer.

References:

CBK, p. 408

HTTPS is used for secure web transactions and is not commonly replaced by SSH.

Users often want to log on to a remote computer. Unfortunately, most early implementations to meet that need were designed for a trusted network. Protocols/programs, such as TELNET, RSH, and rlogin, transmit unencrypted over the network, which allows traffic to be easily intercepted. Secure shell (SSH) was designed as an alternative to the above insecure protocols and allows users to securely access resources on remote computers over an encrypted tunnel. SSH’s services include remote log-on, file transfer, and command execution. It also supports port forwarding, which redirects other protocols through an encrypted SSH tunnel. Many users protect less secure traffic of protocols, such as X Windows and VNC (virtual network computing), by forwarding them through a SSH tunnel. The SSH tunnel protects the integrity of communication, preventing session hijacking and other man-in-the-middle attacks. Another advantage of SSH over its predecessors is that it supports strong authentication. There are several alternatives for SSH clients to authenticate to a SSH server, including passwords and digital certificates. Keep in mind that authenticating with a password is still a significant improvement over the other protocols because the password is transmitted encrypted.

The following were wrong answers:

telnet is an incorrect choice. SSH is commonly used as an more secure alternative to telnet. In fact Telnet should not longer be used today.

rlogin is and incorrect choice. SSH is commonly used as a more secure alternative to rlogin.

RSH is an incorrect choice. SSH is commonly used as a more secure alternative to RSH.

Reference(s) used for this question:

Hernandez CISSP, Steven (2012-12-21). Official (ISC)2 Guide to the CISSP CBK, Third Edition ((ISC)2 Press) (Kindle Locations 7077-7088). Auerbach Publications. Kindle Edition.