Ch. 5-Networking Devices

Describe a bridge.

A bridge is a network device that connects two similar network segments together. Its primary function is to keep traffic separated on either side of the bridge, breaking up collision domains. Traffic is allowed to pass through the bridge only if the transmission is intended for a station on the opposite side. The main reason you would place a bridge in your network would be to connect two segments together or to divided a busy network into two segments.

Describe the proper use of network segmentation when planning and implementing a basic SOHO network.

1.) Determine the requirements 2.) Take environmental considerations.

Understand and describe how DNS works and its purpose

A DNS server binds ip addresses to host names. It translates host names to ip addresses.

Describe VPN concentrators.

A VPN concentrator is a device that accepts multiple VPN connections from remote locations. Although this function can be performed by a router or server, as with the encryption gateways and content filtering devices discussed earlier, the same performance benefits can be derived from dedicating a device to this.

Understand and describe the differences between a hub, a switch (bridge), and a router.

A hub is just a multiport repeater, which just receives and regenerates a signal and then forwards that signal on all active ports without looking at any data. A switch (bridge) is connects multiple segments of a network together (like a hub) but also recognizes frames and pays attention to source and destination MAC address and the port it was received.

Describe a hub.

A hub is the device that connects all the segments of the network together in a star topology Ethernet network. Any transmission received on one port will be sent out all the other ports in the hub, including the receiving pair for the transmitting device, so that Carrier Sense Multiple Access with Collision Detection (CSMA/CD) on the Transmitter can monitor for collisions. Basically, if one station sends a broadcast, all the others will receive it; yet based on the addressing found in the frame, only the intended recipient will actually listen to it. Hubs do not recognize frames and do not pay attention to the source and destination MAC address of the incoming frame or the port on which it was received. Hubs simply send anything they receive on one port out to all the others.

Describe a mulitilayer switch (MLS).

A multilayer switch (MLS) is a computer networking device that switches on Open Systems Interconnection (OSI) Layer 2 like an ordinary network switch but provides routing. A 24 port MLS gives you the best of both worlds. It operates at Layer 3 (routing) while still providing 24 collision domains which a router could not do.

What is a benefit of a multilayer switch (MLS) over a Layer 2 switch?

A multilayer switch provides routing functions.

Describe a proxy server.

A proxy server is a type of server that handles its client-machine requests by forwarding them on to other servers while allowing granular control over the traffic between the local LAN and the Internet. When it receives a request, the proxy will then connect to the specific server that can fulfill the request for the client that wants it. Sometimes the proxy modifies the client's request or a server's response to it—or even handles the client's request itself. It will actually cache or "remember" the specific server that would have normally been contacted for the request in case it's needed another time. This behavior really speeds up the network's function, thereby optimizing its performance. However, proxy servers can also limit the availability of the types of sites that users on a LAN have access to, which is a benefit for an administrator of the network if users are constantly connected to nonwork sites and using all the WAN bandwidth.

What does a repeater do?

A repeater receives a digital signal and reamplifies or regenerates that signal and then forwards the digital signal out all active ports without looking at any data.

Describe a router.

A router is a network device used to connect many, sometimes disparate, network segments together, combining them into what is called an internetwork. A well-configured router can make intelligent decisions about the best way to get network data to its destination. It gather the information it needs to make these decisions based on a network's particular performance data.

Collision domain

All ports on a hub are in the same collision domain. All ports on a switch or a router are in separate collision domains.

Broadcast domain

All ports on a hub or a switch are in the same broadcast domain. All ports on a router are in a separate broadcast domain.

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This device uses hardware addresses to filter a network.

Bridge or switch

Name the types of proxy servers and what they do.

Caching proxy server and web proxy server. A caching proxy server speeds up the network's service requests by recovering information from a client's earlier request. Caching proxies keep local copies of the resources requested often, which helps minimize the upstream use of bandwidth. A web proxy server is usually used to create a web cache. (Think of Google Chrome and Amazon shopping autofilling passwords and billing/shipping information).

Further notes on switches:

Conversely, switches aren't used to create internetworks (they do not break up broadcast domains by default); they're employed to add functionality to a network LAN. The main purpose of a switch is to make a LAN work better—to optimize its performance—providing more bandwidth for the LAN's users. And switches don't forward packets to other networks as routers do. Instead, they only "switch" frames from one port to another within the switched network.

Understand and describe how DHCP works and its purpose

DHCP servers assign IP addresses to hosts. A DHCP server receives a request for IP information from a DHCP client using a broadcast.

Which type of server in your network uses pointer and A records?

DNS server

(Fill in the appropriate layer of the OSI or hub, switch, or router device) Hardware addresses are defined at this layer.

Data link

(Fill in the appropriate layer of the OSI or hub, switch, or router device) Ethernet is defined at these layers.

Data link and physical layers

DHCP servers do what?

Dynamically assign IP addresses to clients.

What is an advantage of using DHCP in a network environment?

Dynamically assigns IP addresses to hosts in the network.

Describe encryption devices.

Encryption devices are appliances that can perform encryption. The advantage of using these devices is that they normally provide more choice of encryption methods and stronger encryption options. They also offload the process from other devices like routers and servers, which is a good thing since the encryption /decryption process is very processor intensive and interferes with other functions that those routers and servers might be performing.

You need a device that can prevent your users from accessing certain web sites . Which device should you install?

Firewall

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This device can never run full duplex.

Hub

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This device creates one big collision domain and one large broadcast domain.

Hub

A network device that is used to connect multiple devices together without segmenting a network is a

Hub

Which device does not aid in network segmentation?

Hub

Describe a DNS server.

It binds IP addresses to hostnames.

What is the primary function of a bridge?

It breaks up collision domains.

Which device is used to segment a network?

router

Describe a load balancer.

It is a special type of router that can send incoming packets to multiple machines hidden behind one IP address. Load-balancing routers follow various rules to determine specifically how they will route network traffic. You can set rules based on the least load, fault tolerance, the fastest response times, or just dividing up (balancing) outbound requests for smooth network operations.

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This device sends and receives information about the Network layer.

Layer 2 - the data link layer.

(Fill in the appropriate layer of the OSI or hub, switch, or router device) A Layer 3 switch or multilayer switch.

Layer 3 - Network layer

List the different names for a router

Layer 3 switch

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This layer creates a virtual circuit before transmitting between two end stations.

Layer 4 - transport layer

Describe a switch.

Like hubs, switches connect multiple segments of a network together but with three significant differences - a switch recognizes frames and pays attention to the source and destination MAC address of the incoming frame as well as the port on which it was received. So, if a switch determines that a frame's final destination happens to be on a segment that's connected via a different port than the one on which the frame was received, the switch will only forward the frame out from the specific port on which its destination is located. If the switch can't figure out the location of the frame's destination, it will flood the frame out every port except the one on which the frame port was received.

Which device should be used if you need to send incoming packets to one or more machines that are hidden behind a single IP address?

Load balancer

Which of the following devices can work at both Layers 2 and 3 of the OSI model?

Multilayer switches

Which of the following is not a term used when making SOHO Internet connections?

NIC

(Fill in the appropriate layer of the OSI or hub, switch, or router device) Logical addressing is used at this layer.

Network layer

Identify the purpose, benefits, and characteristics of using a proxy service.

Purpose:

Further notes on routers:

Remember that routers are really switches; they're actually what we call Layer 3 switches. Unlike Layer 2 switches, which forward or filter frames, routers (Layer 3 switches) use logical addressing and provide what is called packet switching. Routers can also provide packet filtering by using access lists; and when routers connect two or more networks together and use logical addressing (IP or IPv6), this is called an internetwork. Last, routers use a routing table (map of the internetwork) to make path selections and to forward packets to remote networks.

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This device breaks up collision and broadcast domains.

Router

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This device can measure the distance to a remote network.

Router

Which device creates separate collision domains and a single broadcast domain?

Switch

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This device creates many smaller collision domains, but the network is still one large broadcast domain.

Switch or bridge

What advantage does a switch have over a hub?

Switches can run in full-duplex and can break up collision domains. This provides extra bandwidth.

Users arrive at the office after a weekend and the hosts that were shut down over the weekend are restarted but cannot access the LAN or Internet. Hosts that were not shut down are working fine. Where can the problem be?

The DHCP server. If the DHCP server has stopped functioning, it will not hand out IP addresses to hosts that are restarted. However, the hosts that were not shut down still have IP addresses because the lease time has not expired.

Identify the environmental requirements of infrastructure devices.

The temperatures need to be cool and humidity should be neither too damp nor too dry. Heavy duty HVAC systems, ample ventilation, and a humidifying system should be used to keep the environment at optimal levels.

Describe the benefits of using dedicated appliances for certain services.

They can specialize in a specific functionality, provide some fault tolerance or redundancy, provide granular control over the network traffic, offload intensive processes from other devices such as routers and servers.

What role does the "A" record in a Domain Name Service (DNS) server have in your network?

Translate human name to IP addresses

(Fill in the appropriate layer of the OSI or hub, switch, or router device) This layer supports flow control and sequencing.

Transport layer

Routers can use ________________, created by an administrator, to control security on the type of packets that are allowed to enter or exit an interface.

access lists

Routers can provide Layer 2 _________________________ if needed and can simultaneously route through the same interface.

bridging functions

Routers, by default, will not forward any _________ or _________ packets.

broadcast, multicast

Which of the following is NOT an advantage of using appliances to offload services like encryption and content filtering?

less expensive

Routers use the ___________________________________________________ to determine the next hop router to forward the packet to.

logical address in a Network-layer header

Which of the following is among the benefits of a switch?

provides extra bandwidth

Routers can provide _______________________ for specific types of network traffic.

quality of service (QOS)

Which is not an advantage of network segmentation?

reduced congestion

A hub is really a multi-port ______________.

repeater

Layer 3 devices provide connections through ________________.

virtual LANs

What is the most common use for a web proxy?

web cache

Users on your network are saturating your bandwidth because they are using too many non-work-related sites. What device would limit the availability of the types of sites that users on a LAN have access to while providing granular control over the traffic between the local LAN and the Internet?

web proxy