CNAP: Semester 2 ver. 2.1 Introduction to Router Configurations Or, “What The Heck Does That Line Do?” Bob Meyers, CCNA, CCAI Youngstown State University Sept. 2000

RE Meyers, CCNA, CCAI2 Semester 2 Objectives  Configure all routers and PC’s given the teacher topology.  Build and configure a complete network given an IP addressing space and a topology.  Troubleshoot connectivity problems in both topologies.

RE Meyers, CCNA, CCAI3 Learning Problem  It’s hard to accomplish the objectives if you do not understand what each line of a running configuration means to network connectivity.

RE Meyers, CCNA, CCAI4 Learning Problem Solution  Look at each line of a properly configured CNAP Teaching Topology.  Determine how each line contributes to the complete connectivity of the working Teacher Topology.  Examine what IOS programming commands enable the running configuration results.

RE Meyers, CCNA, CCAI5 Teaching Topology think  Don’t even think about starting a project without a clean copy of the topology and interface charts!  Unless you enjoy getting totally lost...

RE Meyers, CCNA, CCAI6 How to use the presentation black  Each slide lists lines of the configuration, with an explanation next to it in black font.  Some of the configuration commands listed are not covered in the CCNA. blue  Those lines will be highlighted in blue, and can be ignored for now.  A brief description will be given of those lines for the curious.  The “notes view” of each slide has the configuration listed and line numbered.  Line numbering does not occur when programming or viewing the configuration. It is done here for convenience!

RE Meyers, CCNA, CCAI7 Configuration for Router Lab-A 1. ! 2. version service timestamps debug uptime 4. service timestamps log uptime 5. no service password-encryption 6. ! 7. hostname Lab-A 8. ! 9. enable secret 5 $1$qBZW$2VeiHaAEdG89KRwYu3LEF1 10. ! 11. no ip subnet-zero 1. Line separator/comments 2. The Cisco IOS version in use. 3. Timestamps debugging messages 4. Time since system reboot. 5. Stops encryption of ALL passwords. 6. Line separator; comments 7. Name given to the router. 8. Separator 9. Encrypted enable mode password. 10. Separator 11. Disables ability to recover addresses lost when sub netting.

RE Meyers, CCNA, CCAI8 Lab-A Configuration (cont.) 12. ip host Lab-B ip host Lab-C ip host Lab-D ip host Lab-E ip host Lab-A ! 12–16. “DNS” resolution. Resolves the router name to the IP addresses that are configured on that router’s interfaces. Allows you to just type in the name of the router when using telnet. The router compares the name to this table and routes the telnet session according to the IP’s listed here. 17. Separator

RE Meyers, CCNA, CCAI9 Lab-A Configuration (cont.) 18. ! 19. ! 20. interface Ethernet0 21. ip address no ip directed-broadcast 23. no shutdown 24. ! 25. interface Ethernet1 26. ip address no ip directed-broadcast 28. no shutdown 29. ! 18. Separator 19. Separator 20. Configure the first Ethernet port, E0 21. Assign IP and subnet mask to Ethernet port E0 22. All IP directed broadcasts are dropped 23. Forces the port to stay open/up. 24. Separator 25. Configure the second Ethernet port, E1 26. Assigns IP and Subnet mask to Ethernet port E1 27. All IP directed broadcasts are dropped 28. Forces the port to stay open/up. 29. Separator

RE Meyers, CCNA, CCAI10 Lab-A Configuration (cont.) 30. interface Serial0 31. ip address no ip directed-broadcast 33. no ip mroute-cache 34. no fair-queue 35. clockrate no shutdown 37. ! 38. interface Serial1 39. no ip address 40. no ip directed-broadcast 41. shutdown 42. ! 30. Configure first serial port S0 31. Assigns an IP and subnet mask to serial port S0 32. All IP directed broadcasts are dropped. 33. Disables IP multicast fast switching. 34. Disables S0 traffic priority management. 35. Sets S0 clock rate at 56KBps 36. Keeps S0 up. Prevents shutdown. 37. Separator 38. Configure second serial interface S No layer 3 address is assigned. 40. All IP directed broadcasts are dropped. 41. S1 is administratively forced to shutdown. 42. Separator

RE Meyers, CCNA, CCAI11 Lab-A Configuration (cont.) 43. router rip 44. network network network ! 48. no ip classless 49. ! 43. Starts RIP routing protocol 44 – 46. Tells the router to send and accept RIP updates to and from the IP networks listed. 47. Separator 48. Discards packets for a subnet that fall within its subnetwork addressing scheme if there is no such subnet number in the routing table and there is no network default route. 49. Separator

RE Meyers, CCNA, CCAI12 Lab-A Configuration (cont.) 50. ! 51. line con password cisco 53. login 54. transport input none 55. line aux line vty password cisco 58. login 59. ! 60. end 50. Line separator 51. Configure the console port. 52. Create the password “cisco” 53. Assign it to the console login 54. VTY sessions only on this port. 55. Configure the first aux port. 56. Allow 5 simultaneous telnet sessions. 57. Create the password “cisco” 58. Assign it to Telnet login sessions. 59. Separator 60. End of configuration.

RE Meyers, CCNA, CCAI13 “Plain English” Line by Line Explanation. 1. Separator 2. Cisco IOS version currently in use. 3. Put a time on each debug message. 4. Start a timer to show how long the router’s been running. 5. Don’t encrypt all the passwords, just do the ones I select as secret. 6. Separator 7. The name given to the router. 8. Separator (again) 9. The privileged mode password after it’s been encrypted for secrecy. 10. Pay attention – this is a line separator. 11. Subnet the way we learned it, and lose the first and last subnets. 12. These are the IP addresses that are used by a router named Lab-B 13. These are the IP’s used by the router named Lab –C 14. Guess who uses these IP addresses? 15. Guess again. 16. Guess one more time. 17. I’m not telling you again about the “separator.” 18. I mean it. 19. I really mean it! 20. Time to configure the first Ethernet port, E Here’s the IP and the subnet for the port. 22. Stop all IP broadcasts right here! 23. Please don’t let E0 shutdown make me crazy wondering why I can’t connect.

RE Meyers, CCNA, CCAI14 “Plain English” Line by Line Explanation. 24. I refuse to answer. 25. Get the second ethernet port, E1, ready for configuration. 26. Give E1 this IP and subnet address. 27. Stop all IP broadcasts from entering this port from the LAN. 28. Don’t shutdown this port. Please? 29. See Get the first serial port, S0, ready for configuration. 31. Assign this IP and subnet mask to S Stop IP broadcast messages! 33. Do not allow fast switching – whatever the heck it is anyway. 34. Don’t use the fancy packet management system on this interface, ‘cause I don’t know how it works – yet. 35. S0 is DCE connection, so it needs to provide the clock rate. 56,000 Bps sounds like a good number. 36. If this interface shuts down I’ll lose my link to all the other routers. So don’t. 37. See Let’s configure the second serial interface, S1. Hey if it’s second, why is it labeled S1? 39. I’m not using it so don’t give it an IP. 40. Stop those pesky IP broadcasts again. Even though I’m still not using this port. 41. Not using it you say? Then shut it down.

RE Meyers, CCNA, CCAI15 “Plain English” Line by Line Explanation. 42. You talking to me? 43. This router will now use RIP as the routing protocol. 44. Accept, and send routing updates, to and from this network address. 45. Do it on this network address, too. 46. Ditto. 47. Still means what it did 5 slides ago! 48. There’s a way to recover the 2 lost addresses when sub netting, but don’t use it till we learn it. 49. Running out of clever retorts for this sucker. 50. Ask one more time and I’m outta here. 51. Configure the console port. 52. Make “cisco” a password. 53. Take the password “cisco” and make it the login challenge when anybody connects to the console port. 54. There are other ways to use the console port, but let’s make a terminal program the only thing the port will recognize. 55. Open the AUX port for configuration. But don’t do anything to it.(?) 56. Configure all incoming Telnet sessions, and limit them to 5 simultaneous connections (0, 1, 2, 3, 4). 57. Create the password “cisco.” You can use any other alphanumeric string if you want. 58. Use “cisco” as the password for all incoming Telnet login challenges. 59. I warned you, didn’t I? 60. Outta here.

RE Meyers, CCNA, CCAI16 The other router configurations can be analyzed the exact same way. Try it for yourself! END