Switches

1
Switches Routers

• Rick Livingood, MA, MCSE, CCNP
• IIUSA Internet Institute

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, 000007, Serial2 C
10.1.1.0 is directly connected, Serial2 R
192.168.1.0/24 120/2 via 10.1.1.2, 000007,
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
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
Converting IP Addresses from Binary to Decimal
Note All 0s indicates a decimal 0, totaling 256
Decimal Values
13
Conversion Example
128 32 16 4 1 181
14
IP Classes
Class A
Class B
Class C
- Network numbers are assigned by ARIN - Host
numbers assigned by Network Administrators
15
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
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
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
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Subnet Mask without Subnets
Network
Host
172.16.2.160
10101100
00010000
10100000
00000010
11111111
11111111
00000000
00000000
255.255.0.0
00000000
00000000
10101100
00010000
Subnet Mask
NetworkNumber
16
172
0
0

• Subnets not in usethe default

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

• Network number extended by eight bits

24
Defining a Subnet Mask
Convert the Number of Segments to Binary Count
the Number of Required Bits Convert the Required
Number of Bits to Decimal (High Order)
1
2
3
Example of Class B Address
6
Number of Subnets
0 0 0 0 0 1 1 0
(3 Bits)
Binary Value
6
42
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 1 0 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
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
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
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
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