Chapter 2

Single-mode is more expensive, has a tighter cladding, and can go much farther distances than multimode. The difference comes in the tightness of the___, which makes a smaller core, meaning that only one mode of light will propagate down the fiber.

cladding

In order for host A to ping host B, you need a ___cable to connect the two switches together.

crossover

The ___cable can be used to connect the following devices: Switch to switch Hub to hub Host to host Hub to switch Router direct to host Router to router The same four wires used in the straight-through cable are used in this cable—we just connect different pins together.

crossover

The function of Ethernet stations is to pass data frames between each other using a group of bits known as a MAC frame format. This provides error detection from a ___

cyclic redundancy check (CRC)

Ethernet uses both ___and ___layer specifications,

Data Link, Physical

To figure out the binary value, put the hex characters into two nibbles and then join them together into a byte. 6 = 0110; A, which is 10 in hex = 1010; so the complete byte would be ___

01101010.

The Type field has ___when the frame is carrying IPv6 data, and when we have IPv4 data, the frame uses ___in the protocol field:

0x86dd, 0x0800

Notice that instead of connecting 1 to 1, 2 to 2, and so on, here we connect pins ___on each side of the cable.

1 to 3 and 2 to 6

Remember that a broadcast is all ___and is sent to all devices.

1s—all Fs in hex—

Okay, once you have the correct cable connected from your PC to the Cisco router or switch console port, you can start your emulation program such as putty or SecureCRT to create a console connection and configure the device. Notice that Bit Rate is set to___, Data Bits to___, Parity to None, and Flow Control is set to None. At this point, you can click Connect and press the Enter key and you should be connected to your Cisco device console port. 2258

9600, 8

The Cisco Three-Layer Hierarchical Model ___

Core, distribution, access

Although rolled cable isn't used to connect any Ethernet connections together, you can use a rolled Ethernet cable to connect a host___ interface to a router console serial communication (COM) port. If you have a Cisco router or switch, you would use this cable to connect your PC, Mac, or a device like an iPad to the Cisco hardware. Eight wires are used in this cable to connect serial devices, although not all eight are used to send information, just as in Ethernet networking.

EIA-TIA 232

___networking uses a protocol called Carrier Sense Multiple Access with Collision Detection (CSMA/CD), which helps devices share the bandwidth evenly while preventing two devices from transmitting simultaneously on the same network medium.

Ethernet

100Base-___ (IEEE 802.3u) Uses fiber cabling 62.5/125-micron multimode fiber. Point-to-point topology; up to 412 meters long. It uses ___connectors, which are media-interface connectors.

FX, ST and SC

___wires are used in straight-through cable to connect Ethernet devices. 2201

Four

___An alternating 1,0 pattern provides a 5 MHz clock at the start of each packet, which allows the receiving devices to lock the incoming bit stream. Start Frame Delimiter (SFD)/Synch The preamble is seven octets and the SFD is one octet (synch). The SFD is 10101011, where the last pair of 1s allows the receiver to come into the alternating 1,0 pattern somewhere in the middle and still sync up to detect the beginning of the data.

Preamble

List all of the fields in a data link pdu___

Preamble, SFD, Destination, Source, Type, Data, FCS

Describe the sections of a MAC address and the information contained in each section.

The MAC, or hardware, address is a 48-bit (6-byte) address written in a hexadecimal format. The first 24 bits, or 3 bytes, are called the organizationally unique identifier (OUI), which is assigned by the IEEE to the manufacturer of the NIC. The balance of the number uniquely identifies the NIC.

Identify the fields in the Data Link portion of an Ethernet frame.

The fields in the Data Link portion of a frame include the preamble, Start Frame Delimiter, destination MAC address, source MAC address, Length or Type, Data, and Frame Check Sequence.

Identify the layers in the Cisco three-layer model and describe the ideal function of each layer.

The three layers in the Cisco hierarchical model are the core (responsible for transporting large amounts of traffic both reliably and quickly), distribution (provides routing, filtering, and WAN access), and access (workgroup connectivity into the distribution layer).

Differentiate types of Ethernet cabling and identify their proper application.

The three types of cables that can be created from an Ethernet cable are straight-through (to connect a PC's or router's Ethernet interface to a hub or switch), crossover (to connect hub to hub, hub to switch, switch to switch, or PC to PC), and rolled (for a console connection from a PC to a router or switch).

Identify the IEEE physical standards for Ethernet cabling.

These standards describe the capabilities and physical characteristics of various cable types and include but are not limited to 10Base-2, 10Base-5, and 10Base-T.

Notice there are two console connections on this new switch—a typical original RJ45 connection, and the newer mini type-B ___console.

USB

You can use full-duplex Ethernet in at least the following six situations: ___

With a connection from a switch to a host With a connection from a switch to a switch With a connection from a host to a host With a connection from a switch to a router With a connection from a router to a router With a connection from a router to a host

802.3___ (Gigabit Ethernet on category 5)

ab

Every Ethernet cable type that's specified by the EIA/TIA has inherent attenuation, which is defined as the loss of signal strength as it travels the length of a cable and is measured in ___

decibels (dB).

But remember that user data is processed at the ___layer, which forwards the requests to the core if needed.

distribution

4. All hosts have ___priority to transmit after the timers have expired.

equal

And full-duplex uses a point-to-point connection between the transmitter of the transmitting device and the receiver of the receiving device. This means that full-duplex data transfers happen a lot ___when compared to half-duplex transfers.

faster

1000Base-T (IEEE 802.3ab) Category 5, ___-pair UTP wiring up to 100 meters long and up to 1 Gbps.

four

1000Base-T UTP wiring (Figure 2-13) requires ___wire pairs and uses more advanced electronics so that each and every pair in the cable can transmit simultaneously. Even so, gigabit wiring is almost identical to my earlier 10/100 example, except that we'll use the other two pairs in the cable.

four

Okay, now suppose you have something like this: 0x6A. This is important because sometimes Cisco likes to put 0x in front of characters so you know that they are a ___value.

hex

The last 24 bits of an Ethernet address represent a ___code. This portion commonly starts with 24 0s for the first card made and continues in order until there are 24 1s for the last (16,777,216th) card made. You'll find that many manufacturers use these same six hex digits as the last six characters of their serial number on the same card.

locally administered or manufacturer-assigned

It's the Data Link layer that's responsible for taking packets from the Network layer and placing them on the network___

medium (cable or wireless).

To convert from binary to hex, just take the byte and break it into ___

nibbles.

The distribution layer is where we want to implement ___for the network because we are allowed a lot of flexibility in defining network operation here.

policies

Multimode is looser and has a larger core so it allows multiple light particles to travel down the glass. These particles have to be ____at the receiving end, so distance is less than that with single-mode fiber, which allows only very few light particles to travel down the fiber. 2303

put back together

Plus, the connection from the router to the switch is a ___cable, as is true for the hosts to the switches.

straight-through

The ___cable is used to connect the following devices: Host to switch or hub Router to switch or hub

straight-through

The core layer is literally the core of the network. At the top of the hierarchy, the core layer is responsible for transporting large amounts of traffic both reliably and quickly. The only purpose of the network's core layer is to ___traffic as fast as possible. The traffic transported across the core is common to a majority of users.

switch

Also, because the transmitted data is sent on a different set of wires than the received data, collisions___.

won't happen

But full-duplex Ethernet uses ___at the same time instead of a ___like half-duplex.

two pairs of wires, single wire pair

The IEEE extended the 802.3 committee to three new committees known as 802.3___(Fast Ethernet),

u

Remember that the new ___port supersedes the ___port if you just happen to plug into both at the same time.

USB, RJ45

Last, remember these important points: There are ___collisions in full-duplex mode. A ____switch port is required for each full-duplex node. ___the host network card and the switch port must be capable of operating in full-duplex mode. The default behavior of 10Base-T and 100Base-T hosts is ___Mbps ___-duplex if the autodetect mechanism fails, so it is always good practice to set the speed and duplex of each port on a switch if you can.

no, dedicated, Both, 10, half

For a straight-through cable it's still 1 to 1, 2 to 2, and so on up to pin 8. And in creating the gigabit crossover cable, you'd still cross___, but you would add ___—pretty straightforward! \

1 to 3 and 2 to 6, 4 to 7 and 5 to 8

Notice that only pins ___are used. Just connect ___and you'll be up and networking in no time. However, remember that this would be a 10/100 Mbps Ethernet-only cable and wouldn't work with gigabit, voice, or other LAN or WAN technology. 2209

1, 2, 3, and 6 1 to 1, 2 to 2, 3 to 3, and 6 to 6

Ethernet was first implemented by a group called DIX, which stands for Digital, Intel, and Xerox. They created and implemented the first Ethernet LAN specification, which the IEEE used to create the IEEE 802.3 committee. This was a ___Mbps network that ran on coax and then eventually twisted-pair and fiber physical media.

10

Half-duplex Ethernet is defined in the original IEEE 802.___ Ethernet specification, which differs a bit from how Cisco describes things.

3

1000Base-___ (IEEE 802.3z) Copper twisted-pair, called twinax, is a balanced coaxial pair that can run only up to 25 meters and uses a special 9-pin connector known as the High Speed Serial Data Connector (HSSDC). This is used in Cisco's new ___Center technologies.

CX, Data

___says Ethernet uses only one wire pair with a digital signal running in both directions on the wire.

Cisco

Identify the binary and hexadecimal equivalent of a decimal number.

Any number expressed in one format can also be expressed in the other two. The ability to perform this conversion is critical to understanding IP addressing and subnetting. Be sure to go through the written labs covering binary to decimal to hexadecimal conversion.

The nodes respond to that jam signal by waiting a bit before attempting to transmit again. ___algorithms determine when the colliding stations can retransmit. If collisions keep occurring after 15 tries, the nodes attempting to transmit will then time out. Half-duplex can be pretty messy!

Backoff

Describe the operation of Carrier Sense Multiple Access with Collision Detection (CSMA/CD).

CSMA/CD is a protocol that helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium. Although it does not eliminate collisions, it helps to greatly reduce them, which reduces retransmissions, resulting in a more efficient transmission of data for all devices.

___This is a packet sent down to the Data Link layer from the Network layer. The size can vary from 46 to 1,500 bytes.

Data

Describe the data encapsulation process and the role it plays in packet creation.

Data encapsulation is a process whereby information is added to the frame from each layer of the OSI model. This is also called packet creation. Each layer communicates only with its peer layer on the receiving device.

___This transmits a 48-bit value using the least significant bit (LSB) first. The ___is used by receiving stations to determine whether an incoming packet is addressed to a particular node. ____can be an individual address or a broadcast or multicast MAC address.

Destination Address (DA)

___is a field at the end of the frame that's used to store the ___answer. The ___is a mathematical algorithm that's run when each frame is built based on the data in the frame. When a receiving host receives the frame and runs the___, the answer should be the same. If not, the frame is discarded, assuming errors have occurred.

Frame Check Sequence (FCS), cyclic redundancy check (CRC), CRC, CRC

Differentiate half-duplex and full-duplex communication and define the requirements to utilize each method.

Full-duplex Ethernet uses two pairs of wires at the same time instead of one wire pair like half-duplex. Full-duplex allows for sending and receiving at the same time, using different wires to eliminate collisions, while half-duplex can send or receive but not at the same time and still can suffer collisions. To use full-duplex, the devices at both ends of the cable must be capable of and configured to perform full-duplex.

Technologies like ___or Fast Ethernet switching are frequently seen in the access layer. I can't stress this enough—just because there are three separate levels does not imply three separate devices! There could be fewer or there could be more. After all, this is a layered approach.

Gigabit

1000Base-___ (IEEE 802.3z) ___-mode fiber that uses a 9-micron core and 1300 nm laser and can go from 3 kilometers up to 10 kilometers.

LX, Single

___802.3 uses a ___field, but the Ethernet_II frame uses a ___field to identify the Network layer protocol. The old, original 802.3 cannot identify the upper-layer protocol and must be used with a proprietary LAN—IPX, for example.

Length or Type, Length, Type

The high-order bit is the Individual/Group (I/G) bit. When it has a value of 0, we can assume that the address is the ___of a device and that it may well appear in the source portion of the MAC header.

MAC address

The EIA/TIA (Electronic Industries Alliance and the newer Telecommunications Industry Association) is the standards body that creates the ___specifications for Ethernet. The EIA/TIA specifies that Ethernet use a registered jack (RJ) connector on unshielded twisted-pair (UTP) cabling (RJ45). But the industry is moving toward simply calling this an 8-pin modular connector.

Physical layer

1000Base-___ (IEEE 802.3z) The implementation of 1 Gigabit Ethernet running over ___fiber-optic cable instead of copper twisted-pair cable, using short wavelength laser. ___fiber (MMF) using 62.5- and 50-micron core; uses an 850 nanometer (nm) laser and can go up to 220 meters with 62.5-micron, 550 meters with 50-micron. 2143

SX, multimode, Multimode

___ a 48-bit MAC address used to identify the transmitting device, and it uses the least significant bit first. Broadcast and multicast address formats are illegal within the ____field.

Source Address (SA)

10GBase-___ (802.3.an) is a standard proposed by the IEEE 802.3an committee to provide 10 Gbps connections over conventional UTP cables, (category 5e, 6, or 7 cables). 10GBase-___ allows the conventional RJ45 used for Ethernet LANs and can support signal transmission at the full 100-meter distance specified for LAN wiring.

T

10Base-___ (IEEE 802.3) 10 Mbps using category 3 ___wiring for runs up to 100 meters.

T, unshielded twisted pair (UTP)

100Base-___ (IEEE 802.3u) 100Base-TX, most commonly known as Fast Ethernet, uses EIA/TIA category ___UTP two-pair wiring. One user per segment; up to 100 meters long. It uses an RJ45 connector with a physical star topology and a logical bus.

TX, 5, 5E, or 6

Understand how to connect a console cable from a PC to a router and switch.

Take a rolled cable and connect it from the COM port of the host to the console port of a router. Start your emulations program such as putty or SecureCRT and set the bits per second to 9600 and flow control to None.

1000Base-___ (Cisco standard) is a Cisco specified standard for Gigabit Ethernet communication. 1000BaseZX operates on ordinary ___-mode fiber-optic links with spans up to 43.5 miles (70 km).

ZX, single

There are several things that should generally be handled at the distribution layer: Routing Implementing tools (such as___), packet filtering, and queuing Implementing ___and network policies, including address translation and firewalls Redistributing between routing protocols, including static routing Routing between VLANs and other workgroup support functions Defining broadcast and multicast domains

access lists, security

Given the function of the core, we can now consider some design specifics. Let's start with some things we don't want to do: Never do anything to slow down traffic. This includes using___, routing between ___and implementing packet___. Don't support workgroup access here. Avoid expanding the core (e.g., adding routers when the internetwork grows). If performance becomes an issue in the core, give preference to ___over expansion.

access lists, virtual local area networks, filtering, upgrades

802.3___ (10 Gbps over fiber and coax).

ae

Full-duplex Ethernet is supposed to offer 100-percent efficiency in both directions—for example, you can get 20 Mbps with a 10 Mbps Ethernet running full-duplex, or 200 Mbps for Fast Ethernet. But this rate is known as an ___rate, which translates as "you're supposed to get" 100 percent efficiency.

aggregate

802.3___(100 Gbps Ethernet)

ba

2. The collision invokes a random ___algorithm.

backoff

Ethernet is a contention-based media access method that allows all hosts on a network to share the same link's ___

bandwidth.

When it's a 1, we can assume that the address represents either a ___

broadcast or multicast address

The access layer controls user and workgroup access to internetwork resources. The access layer is sometimes referred to as the ___layer. The network resources most users need will be available locally because the distribution layer handles any traffic for remote services. The following are some of the functions to be included at the access layer: Continued (from distribution layer) use of access control and policies Creation of separate ___domains (segmentation) Workgroup connectivity into the distribution layer

desktop, collision

The category 5 Enhanced UTP cable can handle speeds up to a ___with a distance of up to ___meters. Typically we'd use this cable for 100 Mbps and category 6 for a gigabit, but the category 5 Enhanced is rated for gigabit speeds and category 6 is rated for 10 Gbps!

gigabit, 100

The next bit is the global/local bit, sometimes called the G/L bit or U/L bit, where U means universal. When set to 0, this bit represents a ___administered address, as assigned by the IEEE.

globally

Even though the IEEE specifications discuss the half-duplex process somewhat differently, it's not actually a full-blown technical disagreement. Cisco is really just talking about a general sense of what's happening with Ethernet. Half-duplex also uses the CSMA/CD protocol I just discussed to help prevent collisions and to permit retransmitting if one occurs. If a hub is attached to a switch, it must operate in ___-duplex mode because the end stations must be able to detect collisions.

half

Figure 2-6 shows four hosts connected to a switch, plus a hub, and definitely try not to use hubs if you can help it! Theoretically all hosts connected to the switch in Figure 2-6 can communicate at the same time because they can run full-duplex. Just keep in mind that the switch port connecting to the hub as well as the hosts connecting to that hub must run at___.

half-duplex

Some main components of a fiber cable are the core and the cladding. The core will ___and the cladding___. The tighter the cladding, the smaller the core, and when the core is small, less light will be sent, but it can go faster and farther!

hold the light, confines the light in the core

Unlike with the 10Base-2 and 10Base-5 networks, each device must connect into a___, and you can have only one host per segment or wire. It uses an RJ45 connector (8-pin modular connector) with a physical star topology and a logical bus.

hub or switch

When a collision occurs on an Ethernet LAN, the following happens: 1. A ___signal informs all devices that a collision occurred.

jam

When a host wants to transmit over the network, it first checks for the presence of a digital signal on the wire. If all is clear and no other host is transmitting, the host will then proceed with its transmission. But it doesn't stop there. The transmitting host constantly monitors the wire to make sure no other hosts begin transmitting. If the host detects another signal on the wire, it sends out an extended ___signal that causes all nodes on the segment to stop sending data—think busy signal.

jam

But when it's a 1, it represents a ___governed and administered address.

locally

The ___is assigned by the IEEE to an organization. It's composed of 24 bits, or 3 bytes, and it in turn assigns a globally administered address also made up of 24 bits, or 3 bytes, that's supposedly unique to each and every adapter an organization manufactures.

organizationally unique identifier (OUI)

But even though a broadcast domain is usually a boundary delimited by ___media like switches and routers, it can also refer to a ___division of a network segment, where all hosts can communicate via a Data Link layer, hardware address broadcast.

physical, logical

The last piece of this cable is the buffer, which is there to ___

protect the delicate glass.

CSMA/CD was actually created to overcome the problem of the collisions that occur when packets are transmitted from different nodes at the same time. And trust me—good collision management is crucial, because when a node transmits in a CSMA/CD network, all the other nodes on the network ___and ___that transmission. Only switches and routers can effectively prevent a transmission from propagating throughout the entire network!

receive, examine

Here's a list of things that we want to achieve as we design the core: Design the core for high reliability. Consider data-link technologies that facilitate both speed and redundancy, like Gigabit Ethernet with ___links or even 10 Gigabit Ethernet. Design with speed in mind. The core should have very little latency. Select routing protocols with lower convergence times. Fast and redundant data-link connectivity is no help if your routing tables are shot!

redundant

The primary functions of the distribution layer are to provide ___access and to determine how packets can access the core, if needed. The distribution layer must determine the ___way that network service requests are handled—for example, how a file request is forwarded to a server. After the distribution layer determines the best path, it forwards the request to the core layer if necessary. The core layer then quickly transports the request to the correct service. 2430

routing, filtering, and WAN, fastest

3. Each device on the Ethernet ____stops transmitting for a short time until its backoff timer expires.

segment

If you're using TCP, the virtual circuit is defined by the source and destination port number plus the source and destination IP address and called a___. Understand that the host just, starting at port number ___ The destination port number defines the upper-layer process or application that the data stream is handed to when the data stream is reliably rebuilt on the receiving host.

socket, 1024 because 0 through 1023 are reserved for well-known port numbers.

The distribution layer is sometimes referred to as the ___layer and is the communication point between the access layer and the core.

workgroup