11.4.3.5 Lab – Troubleshooting Connectivity Issues Answers

11.4.3.5 Lab – Troubleshooting Connectivity Issues (Instructor Version – Recommend Lab)

Instructor Note: Red font color or gray highlights indicate text that appears in the instructor copy only.

Topology

Addressing Table

Objectives

Part 1: Identify the Problem
Part 2: Implement Network Changes
Part 3: Verify Full Functionality
Part 4: Document Findings and Configuration Changes

Background / Scenario

In this lab, the company that you work for is experiencing problems with their Local Area Network (LAN). You have been asked to troubleshoot and resolve the network issues. In Part 1, you will connect to devices on the LAN and use troubleshooting tools to identify the network issues, establish a theory of probable cause, and test that theory. In Part 2, you will establish a plan of action to resolve and implement a solution. In Part 3, you will verify full functionality has been restored. Part 4 provides space for you to document your troubleshooting findings along with the configuration changes that you made to the LAN devices.

Note: The routers used with CCNA hands-on labs are Cisco 1941 Integrated Services Routers (ISRs) with Cisco IOS Release 15.2(4)M3 (universalk9 image). The switches used are Cisco Catalyst 2960s with Cisco IOS Release 15.0(2) (lanbasek9 image). Other routers, switches, and Cisco IOS versions may be used. Depending on the model and Cisco IOS version, the commands available and the output produced might vary from what is shown in the labs. Refer to the Router Interface Summary Table at the end of this lab for the correct interface identifiers.

Required Resources

• 2 Router (Cisco 1941 with Cisco IOS Release 15.2(4)M3 universal image or comparable)
• 1 Switch (Cisco 2960 with Cisco IOS Release 15.0(2) lanbasek9 image or comparable)
• 1 PC (Windows 7 or 8 with terminal emulation program, such as Tera Term)
• Ethernet and Serial cables as shown in the topology

Troubleshooting Configurations

The following settings must be configured on the devices shown in the topology. Paste the configurations onto the specified devices prior to starting the lab.

PC:

IP Address: 192.168.1.10
Subnet Mask: 255.255.255.0
Default Gateway: (leave blank)

Instructor: You may choose to configure the PC settings; otherwise, student will know that the missing default gateway setting is a problem.

S1:

no ip domain-lookup
hostname S1
ip domain-name ccna-lab.com
username admin01 privilege 15 secret 9
$9$lJgfiLCHj.Xp/q$hA2w.oyQPTMhBGPeR.FZo3NZRJ9T1FdqvgRCFyBYnNs
interface FastEthernet0/1
shutdown
interface FastEthernet0/2
shutdown
interface FastEthernet0/3
shutdown
interface FastEthernet0/4
shutdown
interface FastEthernet0/5
duplex full
interface Vlan1
ip address 192.168.1.2 255.255.255.0
line vty 0 4
login local
transport input ssh
line vty 5 15
login local
transport input ssh
crypto key generate rsa general-keys modulus 1024
end

R1:

hostname R1
no ip domain-lookup
ip domain-name ccna-lab.com
username admin01 privilege 15 secret 9
$9$8a4jGjbPPpeeoE$WyPsIiOaYT4ATlJzrR6T9E6vIdESOGF.NYX53arPmtA
interface GigabitEthernet0/0
shutdown
interface GigabitEthernet0/1
ip address 192.168.1.1 255.255.255.0
duplex half
speed auto
no shutdown
interface Serial0/0/0
ip address 10.1.2.1 255.255.255.252
no shutdown
interface Serial0/0/1
no ip address
shutdown
line vty 0 4
login local
transport input ssh
crypto key generate rsa general-keys modulus 1024
end

ISP:

hostname ISP
no ip domain-lookup
interface Serial0/0/0
ip address 10.1.1.2 255.255.255.252
no shut
interface Lo0
ip address 209.165.200.226 255.255.255.255
ip route 0.0.0.0 0.0.0.0 10.1.1.1
end

Part 1: Identify the Problem.

The only available information about the network problem is that the users are experiencing slow response times and that they are not able to reach an external device on the Internet at IP address 209.165.200.226. To determine probable cause(s) for these network issues, you will need to utilize network commands and tools on the LAN equipment shown in the topology.

Note: The user name admin01 with a password of cisco12345 will be required to log into the network equipment.

Step 1: Troubleshoot from the PC.

a. From the PC command prompt, ping the external server IP Address 209.165.200.226.

b. Use the ipconfig command to determine the network settings on the PC.

Step 2: Troubleshoot from S1 using a SSH client session.

Note: Any SSH client software can be used. Tera Term is used in the examples in this lab.

a. SSH to S1 using its IP Address of 192.168.1.2 and log into the switch using admin01 for the user name and cisco12345 for the password.

b. Issue the terminal monitor command on S1 to allow log messages to be sent to the VTY line of your SSH session. After a few seconds you notice the following error message being displayed in your SSH window.

S1# terminal monitor
S1#
*Mar 1 02:08:11.338: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
FastEthernet0/5 (not half duplex), with R1.ccna-lab.com GigabitEthernet0/1
(half duplex).
S1#

c. On S1, issue the show interface f0/5 command to view the duplex setting of the interface.

S1# show interface f0/5
FastEthernet0/5 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0cd9.96e8.8a05 (bia 0cd9.96e8.8a05)
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:35, output 00:00:01, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
849 packets input, 104642 bytes, 0 no buffer
Received 123 broadcasts (122 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 122 multicast, 0 pause input
0 input packets with dribble condition detected
4489 packets output, 361270 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
S1#

Step 3: Troubleshoot on R1 using an SSH client.

a. SSH to R1’s LAN interface and log in using admin01 for the user name and cisco12345 as the password.

b. Issue the terminal monitor command on R1 to allow log messages to be sent to the VTY line of your SSH session for R1. After a few seconds the duplex mismatch message appears on R1’s SSH session.

R1# terminal monitor
R1#
*Nov 23 16:12:36.623: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
GigabitEthernet0/1 (not full duplex), with S1.ccna-lab.com FastEthernet0/5 (full
duplex).
R1#

c. Issue the show interface G0/1 command on R1 to display the duplex setting.

R1# show interfaces g0/1
GigabitEthernet0/1 is up, line protocol is up
Hardware is CN Gigabit Ethernet, address is d48c.b5ce.a0c1 (bia d48c.b5ce.a0c1)
Internet address is 192.168.1.1/24
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half Duplex, 100Mbps, media type is RJ45
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:15, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
641 packets input, 101892 bytes, 0 no buffer
Received 453 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 361 multicast, 0 pause input
1043 packets output, 123698 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
235 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
R1#

d. Issue the ping 209.165.200.226 command on R1 to test connectivity to the external server.

R1# ping 209.165.200.226
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 209.165.200.226, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R1#

e. Issue the show ip interface brief command on R1 to verify interface IP Address settings.

R1# show ip interface brief
Interface                  IP-Address    OK? Method Status           Protocol
Embedded-Service-Engine0/0 unassigned    YES unset  administratively down down
GigabitEthernet0/0         unassigned    YES unset  administratively down down
GigabitEthernet0/1         192.168.1.1   YES manual up               up
Serial0/0/0                10.1.2.1      YES manual up               up
Serial0/0/1                unassigned    YES unset  administratively down down
R1#

f. Issue the show ip route command on R1 to verify the router’s default gateway setting.

R1# show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override

Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.1.2.0/30 is directly connected, Serial0/0/0
L        10.1.2.1/32 is directly connected, Serial0/0/0
     192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, GigabitEthernet0/1
L        192.168.1.1/32 is directly connected, GigabitEthernet0/1
R1#

List the probable causes for the network problems that employees are experiencing.
_____________________________________________________
1. The Default Gateway is not set on the PC.
2. Interface G0/1 is set to Half-Duplex on R1.
3. An incorrect IP Address is set on S0/0/0 on R1.
4. The Gateway of last resort is not set on R1.

Part 2: Implement Network Changes

You have communicated the problems that you discovered in Part 1 to your supervisor. She has approved these changes and has requested that you implement them.

Step 1: Set the Default Gateway on the PC to 192.168.1.1.

Step 2: Set the duplex setting for interface G0/1 on R1 to full duplex.

R1# conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#
*Nov 23 17:23:36.879: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
GigabitEthernet0/1 (not full duplex), with S1.ccna-lab.com FastEthernet0/5
(full duplex).
R1(config)#
R1(config)# interface g0/1
R1(config-if)# duplex full
R1(config-if)# exit
*Nov 23 17:24:08.039: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to
down
R1(config)#
*Nov 23 17:24:10.363: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to
up
*Nov 23 17:24:10.459: %SYS-5-CONFIG_I: Configured from console by console
R1(config)#

Step 3: Reconfigure the IP address for S0/0/0 to IP Address 10.1.1.1/30 on R1.

R1(config)# interface s0/0/0
R1(config-if)# ip address 10.1.1.1 255.255.255.252
R1(config-if)# exit

Step 4: Configure the Gateway of last resort on R1 with a 10.1.1.2 default route.

R1(config)# ip route 0.0.0.0 0.0.0.0 10.1.1.2
R1(config)# end

Part 3: Verify Full Functionality

Verify that full functionality has been restored.

Step 1: Verify that all interfaces and routes have been set correctly and that routing has been restored on R1.

a. Issue the show ip route command to verify that the default gateway has been set correctly.

R1# show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override

Gateway of last resort is 10.1.1.2 to network 0.0.0.0

S*    0.0.0.0/0 [1/0] via 10.1.1.2
      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.1.1.0/30 is directly connected, Serial0/0/0
L        10.1.1.1/32 is directly connected, Serial0/0/0
      192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.1.0/24 is directly connected, GigabitEthernet0/1
L        192.168.1.1/32 is directly connected, GigabitEthernet0/1
R1#

b. Issue the show ip interface s0/0/0 command to verify that the IP Address on S0/0/0 is set correctly.

R1# show ip interface s0/0/0
Serial0/0/0 is up, line protocol is up
  Internet address is 10.1.1.1/30
  Broadcast address is 255.255.255.255
  Address determined by setup command
  MTU is 1500 bytes
  <output omitted>
  IPv4 WCCP Redirect exclude is disabled
R1#

c. Issue the ping 209.165.200.226 command to verify that the external server is reachable now.

R1# ping 209.165.200.226
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 209.165.200.226, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
R1#

d. Issue the show interface g0/1 command to verify that the duplex setting is full duplex.

R1# show interface g0/1
GigabitEthernet0/1 is up, line protocol is up
  Hardware is CN Gigabit Ethernet, address is d48c.b5ce.a0c1 (bia d48c.b5ce.a0c1)
  Internet address is 192.168.1.1/24
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
      reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full Duplex, 100Mbps, media type is RJ45
  output flow-control is unsupported, input flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:04, output 00:00:04, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     559 packets input, 74066 bytes, 0 no buffer
     Received 279 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 208 multicast, 0 pause input
     742 packets output, 81462 bytes, 0 underruns
     0 output errors, 0 collisions, 2 interface resets
     133 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     1 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out
R1#

Step 2: Verify End-to-End connectivity from the LAN PC.

a. Issue the ipconfig command from the command prompt on the PC.

b. Issue the ping 209.165.200.226 command from the CMD window on the PC

Part 4: Document Findings and Configuration Changes

Use the space provided below to document the issues found during your troubleshooting and the configurations changes made to resolve those issues.
____________________________________________________
Documentation will vary but should include the date when troubleshooting was conducted, devices that were tested, commands used along with the output generated by those commands, issues found, and configuration changes made to resolve those issues.

Reflection

This lab had you troubleshoot all devices before making any changes. Is there another way to apply the troubleshooting methodology?
__________________________________________________
Answers may vary. Another way the troubleshooting methodology could be applied would be to complete all 6 steps on a device before moving on to another device. e.g. After you determined that the default gateway was not set on the PC, you would add the default gateway setting and verify functionality. If network issues still exist, you would then move on to the next device, S1 in this example. When the troubleshooting process had been completed on S1 and issues still exist, you would then move on to R1. This process would continue until full network functionality was achieved.

Router Interface Summary Table

Device Configs – Final

Router R1

R1# show run
Building configuration...
Current configuration : 1531 bytes
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
no aaa new-model
memory-size iomem 15
!
no ip domain lookup
ip domain name ccna-lab.com
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
cts logging verbose
!
username admin01 privilege 15 secret 9
$9$8a4jGjbPPpeeoE$WyPsIiOaYT4ATlJzrR6T9E6vIdESOGF.NYX53arPmtA
!
redundancy
!
interface Embedded-Service-Engine0/0
no ip address
shutdown
!
interface GigabitEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface GigabitEthernet0/1
ip address 192.168.1.1 255.255.255.0
duplex full
speed auto
!
interface Serial0/0/0
ip address 10.1.1.1 255.255.255.252
clock rate 2000000
!
interface Serial0/0/1
no ip address
shutdown
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
ip route 0.0.0.0 0.0.0.0 10.1.1.2
!
control-plane
!
line con 0
line aux 0
line 2
no activation-character
no exec
transport preferred none
transport output pad telnet rlogin lapb-ta mop udptn v120 ssh
stopbits 1
line vty 0 4
login local
transport input ssh
!
scheduler allocate 20000 1000
!
end

Switch S1

S1# show run
Building configuration...
Current configuration : 1585 bytes
!
version 15.0
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname S1
!
boot-start-marker
boot-end-marker
!
username admin01 privilege 15 secret 9
$9$lJgfiLCHj.Xp/q$hA2w.oyQPTMhBGPeR.FZo3NZRJ9T1FdqvgRCFyBYnNs
no aaa new-model
system mtu routing 1500
!
no ip domain-lookup
ip domain-name ccna-lab.com
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
interface FastEthernet0/1
shutdown
!
interface FastEthernet0/2
shutdown
!
interface FastEthernet0/3
shutdown
!
interface FastEthernet0/4
shutdown
!
interface FastEthernet0/5
duplex full
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
ip address 192.168.1.2 255.255.255.0
!
ip http server
ip http secure-server
!
line con 0
line vty 0 4
login local
transport input ssh
line vty 5 15
login local
transport input ssh
!
end

Router ISP

ISP# show run
Building configuration...
Current configuration : 1390 bytes
!
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname ISP
!
boot-start-marker
boot-end-marker
!
no aaa new-model
memory-size iomem 15
!
no ip domain lookup
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
cts logging verbose
!
redundancy
!
interface Loopback0
ip address 209.165.200.226 255.255.255.255
!
interface Embedded-Service-Engine0/0
no ip address
shutdown
!
interface GigabitEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface GigabitEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial0/0/0
ip address 10.1.1.2 255.255.255.252
!
interface Serial0/0/1
no ip address
shutdown
clock rate 125000
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
ip route 0.0.0.0 0.0.0.0 10.1.1.1
!
control-plane
!
line con 0
line aux 0
line 2
no activation-character
no exec
transport preferred none
transport output pad telnet rlogin lapb-ta mop udptn v120 ssh
stopbits 1
line vty 0 4
login
transport input none
!
scheduler allocate 20000 1000
!
end