CCNA 2 Review of Cisco CCNA 1

Review will cover… Review the OSI Model Encapsulation LAN Devices & Technologies Transport Layer IP Addressing

Open Systems Interconnected Reference Model Review The OSI Model Open Systems Interconnected Reference Model

Why A Layered Model? Reduces complexity- by dividing complex operations of internetworking into smaller subsets Accelerates evolution Simplifies teaching & learning

Application Layer Application Provides network services (processes) to applications. For example, a computer on a LAN can save files to a server using a ________________ supplied by NOSs like Novell. Network redirectors _________ __________________________________________________. Presentation Session Transport Network Data-Link Physical

Presentation Layer Application Provides __________________ ________________________. Code formatting includes __________________________ Basically, the presentation layer is responsible for representing data so that the source and destination can communicate at the application layer. Presentation Session Transport Network Data-Link Physical

Session Layer Application Provides inter-host communication by __________________________ ____________________________ Session uses dialog control and dialog separation to manage the session Some Session protocols: NFS (Network File System) SQL (Structured Query Language) RPC (Remote Procedure Call ) Presentation Session Transport Network Data-Link Physical

Transport Layer Application __________________________________________________ through the use of TCP. TCP ________________, adding a header with control information for sequencing and acknowledging packets received. The segment header also includes source and destination ports for upper-layer applications TCP is connection-oriented and uses __________________________. UDP is connectionless. UDP __________ __________________________________. Presentation Session Transport Network Data-Link Physical

Network Layer Application Responsible for ________________ _____________________________. Addressing is done through _______ protocols such as _________, IPX, AppleTalk, and DECnet. _______________ is done by using ______________ protocols such as ______________________, and BGP. __________ operate at the Network Layer Presentation Session Transport Network Data-Link Physical

Data-Link Layer Broken into two sublayers – ________ _________________ Application Broken into two sublayers – ________ _________________ Provides access to the media Handles error notification, network topology issues, and physically addressing the frame. Media Access Control through either... Deterministic— Non-deterministic— Presentation Session Transport Network Data-Link Physical

Physical Layer Provides electrical and functional means for activating and maintaining links between systems. Ex: ____________________ Includes the medium through which bits flow. Media can be... Application Presentation Session Transport Network Data-Link Physical

Encapsulation Example Application You type an email message. SMTP takes the data and passes it to the Presentation Layer. Presentation codes the data as ASCII and adds a header Session establishes a connection with the destination for the purpose of transporting the data and adds a header Presentation Session Transport Network Data-Link Physical

Encapsulation Example Transport segments the data using TCP and hands it to the Network Layer for addressing also adding a header Network addresses the packet using IP and adds a header of its own. Data-Link then encaps. the packet in a frame and addresses it for local delivery (MACs). This layer adds both header and a trailer The Physical layer sends the bits down the wire. Application Presentation Session Transport Network Data-Link Physical

LAN Devices and Technologies What does it do? Connects LAN segments; Filters traffic based on MAC addresses; and Separates collision domains based upon MAC addresses. What layer device?

Devices What does it do? What layer device? Since it is a multi-port bridge, it However, switches also offer

Devices What does it do? What layer device? Concentrates LAN connections from multiple devices into one location ________________ (a hub is a multi-port repeater)

Devices What layer device? What does it do? Re-encapsulates the packet in the appropriate frame format and _____________ ____________________ Uses ___________ addressing (i.e. IP addresses) to determine the path

Media Types

Three Most Commonly Used Today in Networking LAN Technologies Three Most Commonly Used Today in Networking

Ethernet/802.3 100 Mbps Ethernet is also known as ______ Ethernet. 10BASE-5, 10BASE-2, and 10BASE-T Ethernet are considered _______________ Ethernet. 100 Mbps Ethernet is also known as ______ Ethernet. 100BASE-TX, which is __________________, and 100BASE-FX, which is ______________________ based Gigabit Ethernet standards represent transmission using both fiber and copper media. ______________________________ (IEEE 802.3z) specifies a 1-Gbps full duplex over optical fiber The 1000BASE-T standard (IEEE 802.3ab) uses a media of Category 5 or higher UTP.

Ethernet/802.3 Ethernet is broadcast topology. What does that mean? Every devices on the Ethernet segment sees every frame. __________________________________________________________________________________________________: FFFF.FFFF.FFFF What is the main network traffic problem caused by Ethernet broadcast topologies? Ethernet topologies are also shared media What does this mean? Collisions are resolved or minimized using what device?

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) How CSMA/CD works: A node needing to transmit listens for activity on the media. If there is none, it transmits. The node continues to listen. A collision is detected by a constant elevation in voltage (a bit can only be a 0 or a 1--it cannot be a 2) The node generates a jam signal to tell all devices to stop transmitting for a random amount of time (back-off algorithm). When media is clear of any transmissions, the node can attempt to retransmit.

Address Resolution Protocol In broadcast topologies, we need a way to resolve ____________________________ ________________________ ARP is protocol where the sending device sends out a broadcast ARP request which says, “What’s your MAC address?” If the destination exists on the same LAN segment as the source, then ______________ ____________________________________

ARP cont… If the destination and source are separated by a router, the router will not forward the broadcast (an important function of routers). Router replies ________________________.

Transport Layer A Quick Review

Transport’s Two Protocols TCP- Transmission Control Protocol Synchronization of the connection ____________________________ Connection-oriented _____________________________ “Slow down, you’re overloading my memory buffer!!” _______________________________________________ Reliability & Error Recovery _________________: “How much data can I send before getting an acknowledgement?” Retransmission of lost or unacknowledged segments Applications: Email File Transfer

Transport’s Two Protocols cont… UDP User Datagram Protocol _____________________ ______________________ Applications: Routing Protocols Streaming Audio Video Conferencing

IP Addressing Subnetting Review

Logical Addressing At the network layer, we use logical, hierarchical addressing. With Internet Protocol (IP), this address is a ______ addressing scheme divided into ________ octets. Do you remember the classes 1st octet’s value? Class A: Class B: Class C: Class D: 224 - 239 (multicasting) Class E: 240 - 255 (experimental)

Network vs. Host Class A: 27 = 126 networks; 224 > 16 million hosts N H Class B : 214 = 16,384 networks; 216 = 65,536 hosts N H Class C : 221 > 2 million networks; 28 = 256 hosts N H

Why Subnet? Remember: we are usually dealing with a broadcast topology. Can you imagine what the network traffic overhead would be like on a network with 254 hosts trying to discover each others MAC addresses? Subnetting allows us to _________________ ___________________________, thereby improving network performance.

Borrowing Bits In order to subnet, we must borrow bits from the ______________ portion on the IP address. First, we must determine how many subnets we need and how many hosts per subnet. We do this through the power of 2 For example, I need 8 usable subnets from a Class C: How many host do we have?

Subnet Mask We determine the subnet mask by adding up the decimal value of the bits we borrowed. In the previous Class C example, we borrowed 4 bits. Below is the host octet showing the bits we borrowed and their decimal values. 128 64 32 16 8 4 2 1 1 We add up the decimal value of these bits and get ___. That’s the last non-zero octet of our subnet mask. So our subnet mask is ______________________

You should be able to: Calculate the last non-zero octet when given the number of bits borrowed. Determine the number of bits borrowed given the last non-zero octet. Determine the amount of bits left over for hosts and the number of host addresses available.

CIDR Notation Classless Interdomain Routing is a method of representing an IP address and its subnet mask with slash followed by a number. For example: 192.168.50.0/27 What do you think the 27 tells you? Also, you know 192 is a _________________________

Here’s a shortcut… Magic Number Given the IP address and the subnet mask, you can determine the first usable subnet quickly. By knowing the…. Magic Number

Magic Number Quick way to determine the first usable subnet. Generated by subtracting the last non-zero octet of the subnet mask from the number 256 In the previous example: 192.168.50.0/27 We figured out the subnet mask was: 255.255.255.224 224 is the ___________________________ The magic number is 256 - 224 = 32, so the

202.151.37.0/26 Subnet mask? Bits borrowed? Magic Number? First useable subnet address? Second (and last) useable subnet address?

194.53.45.0/29 What kind of address is 194.53.45.26? Magic number is Subnets are So 194.53.45.26 belongs to the What broadcast address would this host use to communicate with other devices on the same subnet?