1. TROUBLESHOOTING Network infrastructure maintenance and troubleshooting

2. Talking to the customer Customer: –I have written a letter in Word but I can’t print it out because the mouse is stuck Help desk: – If your mouse is stuck how could you write the letter? Customer: –The computer is working fine but the printers error lamp flash because the mouse is stuck Help desk: ????

3. Network maintenance Hardware and software installation and configuration Troubleshooting problem reports Monitoring and tuning network performance Planning for network expansion Documenting the network and any changes made to the network Ensuring compliance with legal regulations and corporate policies Securing the network against internal and external threats

4. Network maintenance goals Reduced network downtime –Discovering and preventing problems before they happen More cost-effectiveness –Performance monitoring and capacity planning allows decision makers to make efficient budgeting decisions. Better alignment with business objectives – Time and resources are allocated to processes based on their importance to the business Higher network security –Continued attention to network security and prevention techniques including monitoring

5. Proactive Versus Reactive Structured tasks (Proactive) –Performed as a predefined plan –Often a maintenance policy/model is used –Planning for changes and the future Interrupt driven tasks (Reactive) –Resolving issues as they are reported –Often little or no planning

6. Maintenance models Many companies follow a well-known maintenance model –Trouble tickets –Up-to-date documentation –All changes described –Knowledge database ModelExplanation ITILIT Infrastructure Library FCAPSFault, Configuration, Accounting, Performance and Security management PPDIOOPrepare, Plan, Design, Implement, Operate and Optimize

7. ITIL IT Infrastructure Library Set of practices for IT service management –(ITSM) Focuses on aligning ITSM with the needs of business Current version ITIL version 3 ITIL certification required at some companies Developed by UK government Widely used as formalized way of doing ITSM

8. FCAPS Developed by ISO for telecommunication network management Fault management –Recognize, isolate, correct and log faults Configuration management –Gather and store configurations of devices Accounting management –Billing management Performance management –Monitor efficiency of network and prepare for the future Security management –Controlling access to the network (authentication)

9. PPDIOO –Developed by Cisco for network and service management –Network lifecycle

10. Troubleshooting Using a structured approach StepDescription Collect informationA problem report often lacks sufficient information Examine collected informationFor example comparing to baseline information. (If available) Eliminate potential causesBased on knowledge of network and collected information - start to eliminate causes. Hypothesize underlying causeAfter eliminating causes hypothesize the most likely cause of the problem. Verify hypothesisTest if the hypothesize resolve the problem

11. Troubleshooting

12. Different approaches –Top-down Start with the application (Internet explorer) –Bottom-up Start with the physical (Link established to network) –Divide and conquer Is it possible to ping. If yes then … if no then …

13. Troubleshooting Follow the path of traffic –Step 1: Is the switch switching the packet –Step 2: Can the Router be pinged from the PC –Step 3: Is the Router routing the packet –Step 4: Is the switch switching the packet –Step 5: Is the server receiving the packet

14. Troubleshooting Component swapping

15. T-shoot example Problem report from user at client 3: –I have no connection to the Internet

16. T-shoot example Very short problem report. –Could be almost anything!! Collect information –Network drawing good documentation –Try and talk to the user – if available Are other users experiencing symptoms? –In this case it is after business hours – so no info –We can’t find more info before we visit the customer's premises Where should we go??

17. T-Shoot example We have to go to building 3 Client 3 and verify the problem For example by opening the browser and connecting to google.com and search for applepie

18. T-Shoot example Follow the path of the traffic –A chain of events. Analyze prerequisites –The PC needs the following prerequisites to be successfully connected to the Internet 1.A valid IP address from the DHCP server 2.A valid IP address for a working DNS server 3.Connection to the Internet through the network Examine each prerequisite for itself –Simplify T-shooting

19. The DHCP chain DHCP discover packet sent from client DHCP discover packet Received by Router And relayed to 192.168.0.2 R3 routes packet To R2 R2 routes packet To R1 R1 routes packet To server 1 DHCP server find a free IP address in the 192.168.210.0/24 pool DHCP server sends DHCP Offer back to the client Vi R3 DHCP relay

20. DHCP chain tools IPCONFIG /ALL –See detailed IP configuration on host IPCONFIG /RELEASE –Release IP address leased from DHCP server IPCONFIG /RENEW –Request DHCP lease from DHCP server PING 192.168.0.2 –Is it possible to reach the DHCP server TRACERT –d 192.168.0.2 –How far – in routers – will the packets go

21. DHCP chain tools Logon to the DHCP server and check –Is the DHCP service running –Does a scope exist for 192.168.210.0/24 Is the scope active Are the any free IP addresses for leasing

22. DHCP chain tools Are the host configured as a DHCP client Are the DHCP relay on R3 configured correctly If the host has no IP address and it’s impossible to lease one –It is possible to temporarily give the host an IP address (Possible IP address conflict !!! ) –For example IP Address192.168.210.201 Subnet mask255.255.255.0 Default gateway192.168.210.1 DNS server192.168.0.2

23. The DNS chain DNS request sent to DNS server Ie. www.ascom.no DNS Server tryes to Resolve www.asom.no If the DNS can’t resolve www.ascom.no it will ask It’s forwarder or a DNS root-server (Depending on configuration) Answer from Internet returns DNS server returns answer to client

24. DNS chain tools NSLOOKUP –Test DNS server resolver If known test DNS servers own zone-records –For example NSLOOKUP server1.ascom.local Logon to the DNS server –Check DNS service running –Check Internet connectivity from DNS server Ping 8.8.8.8 –Check forwarder and if root-server IP addresses are configured properly

25. The Internet chain Clints sends HTTP: request Packet to www.ascom.no’s IP Address Answer from www.ascom.no

26. The Internet chain PING to the internet –For example: PING 8.8.8.8 TRACERT to the internet –For example: TRACERT –d 8.8.8.8 Check routing tables on routers –The routers has to know all routes on the way –Check default route 0.0.0.0/0 Is NAT/PAT working properly on R1

27. T-shoot Conclusion While testing one chain after another –The problem will be isolated and we focus on one chain –Dissect the suspected chain and find the problem using Divide and conquer Bottom-up Top-down Shoot from the hip Swapping devices It could of course be a misconfigured browser

28. Thank you for participating