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Switches & Routers

Switches & Routers. Section Objectives. Overview of Switches and Routers in a Network Environment Switch Configuration Routing Basics and Configuration Displaying Router Information Troubleshooting Routers and Switches. Layer 3 (IP) Basics.

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Switches & Routers

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  1. Switches & Routers

  2. Section Objectives • Overview of Switches and Routers in a Network Environment • Switch Configuration • Routing Basics and Configuration • Displaying Router Information • Troubleshooting Routers and Switches

  3. Layer 3 (IP) Basics • Provides ability to address devices with a logical address and route traffic not locally attached • Logical addresses are applied to source and destination nodes or devices • Paths are determined to forward data from a local device to a remote device on another network

  4. Router Functionality Network A Network B e1 e0 Routing Table Network A e0 Network B e1 Routers Separate Broadcast Domains

  5. Why a Logical Address • Hierarchical addresses provide reachability across boundaries called subnets • Similar to the phone system with area codes to differentiate geographical regions or zip codes to indicate different cities and towns • A hierarchical logical computer address contains a network identifier and host or unit identifier

  6. Network Segments • The size of a network dictates traffic load and potential for overload • As growth overwhelms a network (similar to cars crowding a highway), segments can be created to off load traffic • Each new segment is autonomous of other network segments • Without segmentation, all addressing would be done through a flat addressing scheme (MAC addressing) overwhelming segmentation discovery devices (routers)

  7. Connectivity Between Segments • Segments can communicate through devices that determine a path from one network to another over communications lines • Devices (routers) can determine the best path in the case of multiple paths • Paths or routes are stored in routing tables 172.16.0.0/24 is subnetted, 1 subnets C 172.16.1.0 is directly connected, Ethernet0 10.0.0.0/24 is subnetted, 2 subnets R 10.2.2.0 [120/1] via 10.1.1.2, 00:00:07, Serial2 C 10.1.1.0 is directly connected, Serial2 R 192.168.1.0/24 [120/2] via 10.1.1.2, 00:00:07, Serial2 Portion of a Routing Table

  8. Network Layer Addressing • Routers use a portion of the address to determination Network identification • All hosts or devices within a given network segment are identified by a host portion of the address • IP Addresses 172.16.10.100 Network ID Host ID

  9. Path Determination • Network layer determines BEST path from source to destination • A router examines reported paths over links, determining best path from metrics associated with each path Best Path

  10. Data IP Header Detail Version 4 Header Length 4 Type of Service 8 Total Length 16 Identification 16 Flags 3 Fragment Offset 13 Time to Live 8 Protocol (Upper Level) 8 Header Checksum 16 Source IP Address 32 Destination IP Address 32 IP Options Variable Data Padding (If Needed)

  11. IP Address Numbering • IP Addresses are 32 bits in length Network Host . . . 172 16 122 204 10101100 00010000 01111010 11001100 Each Octet is 8 bits in length, representing a byte

  12. 8 Bits 1 1 1 1 1 1 1 1 128 64 32 16 8 4 2 1 255 Decimal Value Converting IP Addresses from Binary to Decimal Note: All 0s indicates a decimal 0, totaling 256 Decimal Values

  13. 8 Bits 1 0 1 1 0 1 0 1 128 64 32 16 8 4 2 1 255 Decimal Value Conversion Example 128 + 32 + 16 + 4 + 1 181

  14. N N N H N N H N H H H H IP Classes Class A Class B Class C - Network numbers are assigned by ARIN - Host numbers assigned by Network Administrators

  15. N H H H Class A Notes • Address range 1 to 126 • Address 10 is reserved as a private address • Address 127 is reserved for loopback purposes • First bit begins with a 0 (zero) 0

  16. N N H H Class B Notes • Address range 128 to 191 • Address 172.16 to 172.31 is reserved as a private address range • First two bits begin with a 10 10

  17. N N N H Class C Notes • Address range 192 to 223 • Address 192.168 is reserved as a private address range • First three bits begin with a 110 110

  18. Reserved Address Space • 0s (zeros) in the host portion of the address space is reserved for the network number • Example: 172.16.0.0 • 1s in the host portion of the address is reserved for the broadcast address • Example: 172.16.255.255

  19. A Case for Subnetting • The original IP addressing scheme was sufficient for the early days of the internetworking environment • As the Internet grew in the 1990s, addressing, using classful addressing became impractical • Subnetting (classless) addressing became the answer for address space depletion

  20. Subnetting • Subnetting borrows host bits to increase the number of networks • The number of hosts is reduced in proportion to the number of bits borrowed

  21. A Subnetted Network 172.16.3.0 172.16.4.0 172.16.5.0 172.16.1.0 172.16.2.0 Original Network 172.16.0.0

  22. Subnet Mask without Subnets Network Host 172.16.2.160 10101100 00010000 00000010 10100000 11111111 11111111 00000000 00000000 255.255.0.0 00000000 00000000 10101100 00010000 Subnet Mask NetworkNumber 172 16 0 0 • Subnets not in use—the default

  23. Subnet Mask with Subnets Subnet Network Host 172.16.2.160 10101100 00010000 00000010 10100000 11111111 11111111 00000000 11111111 255.255.255.0 10101100 00010000 00000010 00000000 128 192 224 240 248 252 254 255 NetworkNumber 172 16 2 0 • Network number extended by eight bits

  24. Defining a Subnet Mask 1 Convert the Number of Segments to Binary Count the Number of Required Bits Convert the Required Number of Bits to Decimal (High Order) 2 3 Example of Class B Address 6 Number of Subnets 0 0 0 0 0 1 1 0 (3 Bits) Binary Value 4+2 = 6 Convert to Decimal 11111111 11111111 11100000 00000000 255 . 255 . 224 . 0 Subnet Mask Ignore the first bit borrowed, add the additional bits borrowed to determine the number of new subnets

  25. Defining Subnet IDs 255 255 224 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10 0 0 0 0 0 0 0 0 0 0 0 0 00000000 = 0 00100000 = 32 01000000 = 64 01100000 = 96 10000000 = 128 10100000 = 160 11000000 = 192 11100000 = 224 Evaluate the bit patterns established within the subnetted region 2 3

  26. Shortcut to Defining Subnet IDs 11000000 1 List the Number of Bits (High Order) Used for Subnet Mask Convert the Bit with the Lowest Value to Decimal Increment the Value for Each Bit Combination 64 2 3 0 + 64 = 64 + 64 = 128 + 64 192 w.x.64.1 w.x.127.254 w.x.128.1 w.x.191.254

  27. 00000000 = 0 00100000 = 32 01000000 = 64 01100000 = 96 10000000 = 128 10100000 = 160 11000000 = 192 11100000 = 224 Defining Host IDs for a Subnet Subnet IDs Host ID Range Invalid x.y.32.1 – x.y.63.254 x.y.64.1 – x.y.95.254 x.y.96.1 – x.y.127.254 x.y.128.1 – x.y.159.254 x.y.160.1 – x.y.191.254 x.y.192.1 – x.y.223.254 Invalid • Each Subnet ID Indicates the Beginning Value in a Host Range • The Ending Value Is One Less Than the Beginning Value of the Next Subnet ID

  28. 172.16.3.0 172.16.4.0 172.16.1.0 172.16.2.0 Network to Network Connectivity • Router strips off the data link header • Examines the network layer address • Consults the routing table to find the interface for the network 1 2 3

  29. Application Application Presentation Presentation Session Session Transport Transport Network Network Network Network Network Data Link Data Link Data Link Data Link Data Link Physical Physical Physical Physical Physical Network-Layer Protocol Operations X Y C A B A B C Each router provides its services to support upper-layer functions

  30. Routed Versus Routing Protocols • Routed Protocols – Any network protocol run on a workstation as a part of the network operating system that provides networking capabilities (Ex: TCP/IP) • Routing Protocols – Protocols run on a router to provide the ability for the router to share path information (Ex: RIP, IGRP)

  31. Routing Protocols • Interior Routing Protocols – support the sharing of routes or paths within the internal internetwork • (Ex: RIP, IGRP, EIGRP, OSPF) • Exterior Routing Protocols – support the sharing of routes or paths across large internetworks, such as the Internet • (Ex: BGP and EGP)

  32. Routing Metrics • All routing protocols utilize metrics to characterize best path information • Hop Count • Bandwidth • Delay • Load • Reliability • Ticks (Novell) • Cost – generic definition of metric information

  33. Static versus Dynamic Routes • Static routes are established by a network administrator and manually input directly into the routing table • Dynamic routes are learned through the use of a Routing Protocol. Dynamic routes are adaptive. Changes to path availability or establishment of new paths are automatically shared with other routers

  34. Routers • A Router is a computer, with similar functionality • Forwards packets, from incoming interface to outgoing interfaced, based on best path as determined by routes available in the routers Routing Table • Segments a LAN into separate Broadcast Domains • Must be used when connecting LANs across wide area network environment

  35. Primary Memory DRAM SIMM Flash Card Slot System Code Flash or PROM Shared Memory Fixed DRAM Boot ROMS AUX Ethernet Serial Console Typical Router System Board Layout Polarization Notch Memory Types: RAM/DRAM NVRAM Flash Memory ROM

  36. Typical Cisco Motherboard for a 2500 Series

  37. Sources For Configuring VTY 0 - 4 Interfaces Console Port Auxiliary Port TFTP Server Network Management Station Dial-in Access with modems

  38. Router and Switch Configuration

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