© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Troubleshooting Your Network Networking for Home and Small Businesses – Chapter 9

ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public The Troubleshooting Process  Most experienced people rely on instinct to help troubleshoot  Important to maintain documentation to help in the process – record problems encountered – what steps were taken to determine the cause – what steps have been taken to make sure it doesn’t occur again –Document all steps even the ones that did not solve the issue This becomes a valuable reference in the future

ITE PC v4.0 Chapter 1 3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public The Troubleshooting Process  Step 1 – Gather information – Question the individual who has the problem end user experiences observation by the user error messages  Step 2 – Collect information about affected equipment –Gathered from documentation –look at logged files – changes made to equipment configurations – warranty information – network monitoring tools used for larger networks

ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Troubleshooting Techniques  Use OSI layered approach  Top-down – start at application layer – work down until faulty error occurs –Is it just one application failing?  Bottom-up – start at physical layer and work up –hardware failures –Cabling connection problems (loose cable, wrong cable)  Divide and Conquer – begins in the middle layers –Works up or down –Start at network layer, verify IP config – based on experience

ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Approaches to Troubleshooting  Trial and Error – relies on an individual’s knowledge to determine most probably cause – educated guess based on past experiences – if it doesn’t work, try, try again until problem is solved –Could be extremely fast Depends on experiences of the troubleshooter  Substitution – problem assumed to be caused by a specific part – the solution – replace the part – used for inexpensive items cables, NICs, etc

ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Approaches to Troubleshooting

ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Utilities Used to Detect Physical Problems  Use your senses  Sight—cables not connected or in the wrong order  Smell—overheating  Touch—overheating  Hearing—sounds of fans running too much, or grinding of the hard drive

ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 9.2.2Utilities Used to Verify TCP/IP Connectivity  IP Config – checks to make sure correct IP and subnet mask  Ping – verifies connectivity to other hosts  Tracert – traces the route of the packet –Determines the location of delay for a packet traversing the internet  Netstat – show what networks are active  Nslookup – asks the name server for information to determine if a DNS server is providing name resolution

ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public IP CONFIG commands  Ipconfig - displays current IP configuration – IP address – Subnet Mask – Default Gateway  Ipconfig /all – displays additional information –MAC Address –DHCP server and lease info (if enabled) – DNS information  Ipconfig /release – used with DHCP – release IP address  Ipconfig /renew – used with DHCP – refreshes IP (requests IP configuration from a DHCP Server

ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public PACKET TRACER ACTIVITY ACTIVITY 9.2.3

ITE PC v4.0 Chapter 1 11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public The Ping Command  Used to determine whether or not the host is reachable  Can be used with either an IP address of name of destination  Echo request – ping sent  Echo reply – destination host responds  Ping issues – able to ping both IP and name, but unable to access application problem likely at destination host –Unable to ping both IP and name network connectivity problem if able to ping default gateway, problem not at local level –Ping to IP works, but name doesn’t Problem is with DNS

ITE PC v4.0 Chapter 1 12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public PACKET TRACER ACTIVITY ACTIVITY 9.2.4

ITE PC v4.0 Chapter 1 13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public The Tracert Command  Shows each hop along the way  Tells how long it takes for the packet to be sent and get a response (round trip time)  30 hops – network/user deemed unreachable – default settings – can be changed by adjusting the –h parameter

ITE PC v4.0 Chapter 1 14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public The Netstat Command  Views open (running) connections on a host  Used when performance appears to be compromised  Informs user about: – protocols – local address – port numbers – connection state

ITE PC v4.0 Chapter 1 15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public The Nslookup Command  Allows end user to look up information about DNS name in the DNS server  Used as a troubleshooting tool to see if DNS server has the correct IP with the correct name

ITE PC v4.0 Chapter 1 16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 9.3.1Hardware and Connection Issues in Wired & Wireless Networks  Use divide-and-conquer technique  To determine where the problem exists: – ping from wireless client to default gateway to verify wireless is working properly – ping from wired client to default gateway to verify that wired is working properly – ping wireless client to wired client to verify that the integrated router is functioning properly

ITE PC v4.0 Chapter 1 17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public LED Indicators  Used to show activity or to convey information  Security LED – solid green = security enabled  Link Lights – solid green = plugged in with no traffic – flashing green = plugged in with traffic – amber = making adjustments  Power LED – solid green = operational

ITE PC v4.0 Chapter 1 18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Cable Issues  One of the most common problems  Check for: – correct cable type KNOW WHEN TO USE EACH KIND OF CABLE –Straight through—devices that aren’t the same (EX: computer to switch) –Cross over—devices that are the same (EX: computer to computer) –Rollover—used to configure a router through the console port – improper cable termination –Too much untwisting – too long of cable runs – verify correct ports – protect cables from damage

ITE PC v4.0 Chapter 1 19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Cable Issues Rollover cables use this kind of plug to plug into the comport of the computer

ITE PC v4.0 Chapter 1 20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Radio Problems with a Wireless Network  What if... – the wireless client is unable to connect to the access point but wired can  Possible fixes: – check wireless standards being used – check channels – check signal strength may be too far away from AP – check for outside interference –Check WEP key is correct – check available bandwidth too many clients on one channel

ITE PC v4.0 Chapter 1 21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Association and Authentication Issues  The following three settings must match on the client and access point for a wireless connection to occur SSID –make sure client is configured with the correct SSID Check Authentication – open (by default) – might have be changed – check to make sure the correct key is being used Encryption – key needed by the client

ITE PC v4.0 Chapter 1 22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public DHCP Problems  Make sure the IP address of the client is on the same network as the ISR  If both client and access point are not on the same network, use release and renew

ITE PC v4.0 Chapter 1 23 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ISR Router to the ISP Problems  Wired and Wireless devices can connect to each other, but not the Internet... Why??  May be a connection between the access point and the ISP – check out the router status page – check physical connections (including indicator lights) – verify passwords – may be that the Internet site is just down

ITE PC v4.0 Chapter 1 24 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Documentation  Set a performance baseline – do this just after the network is installed and running efficiently  When documenting a problem, include the following – initial problem – steps taken – result of the steps – determined cause of problem – how the problem was resolved – preventive measures taken –Keep a record of system upgrades and software versions

ITE PC v4.0 Chapter 1 25 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Using the Helpdesk  Provides assistance for the end user to help fix a problem – via – via live chat – via phone  Use of remote access – help desk takes control of your machine  Inform the help desk of the following: – symptoms – who had the problem – when it happened – steps taken – results of steps taken

ITE PC v4.0 Chapter 1 26 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary  Effective troubleshooting combines instinct, experience, and structured techniques to identify, locate, and correct network or computer problems.  Documentation is essential in effective troubleshooting, and should contain baseline information about the network.  A large proportion of networking problems relate to physical components.  Many networking problems can be identified with software utilities such as ping, tracert, and netstat.  In a network containing both wired and wireless connections, it is important to isolate the problem to either the wired or wireless network.

ITE PC v4.0 Chapter 1 27 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public