2.1.2.5 Packet Tracer – Troubleshooting Serial Interfaces
Feb 06, 2017 Router# interface serial 0/0/0. Specifies the serial interface and enters interface configuration mode. For configuring IP Address for any interface you must be in global configuration mode and then enter to the line configuration mode of required interface. In this case we are going to set ip address for serial 0/0/0 interface. Assuming you are at user exe mode. Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube.
Packet Tracer – Troubleshooting Serial Interfaces (Answer Version)
Answer Note: Red font color or Gray highlights indicate text that appears in the Answer copy only.
Topology
2.1.2.5 Packet Tracer – Troubleshooting Serial Interfaces
Addressing Table
Device | Interface | IP Address | Subnet Mask | Default Route |
Telco | S0/0/0 (DCE) | 64.100.34.17 | 255.255.255.252 | N/A |
S0/0/1 (DCE) | 64.100.34.21 | 255.255.255.252 | N/A | |
S0/1/0 (DCE) | 64.100.34.25 | 255.255.255.252 | N/A | |
S0/1/1 (DCE) | 64.100.34.29 | 255.255.255.252 | N/A | |
R1 | S0/0/0 | 64.100.34.18 | 255.255.255.252 | 64.100.34.17 |
R2 | S0/0/1 | 64.100.34.22 | 255.255.255.252 | 64.100.34.21 |
R3 | S0/0/0 | 64.100.34.26 | 255.255.255.252 | 64.100.34.25 |
R4 | S0/0/1 | 64.100.34.30 | 255.255.255.252 | 64.100.34.29 |
Objectives
Part 1: Diagnose and Repair the Physical Layer
Part 2: Diagnose and Repair the Data Link Layer
Mkvtoolnix 36 0 0 g. Part 3: Diagnose and Repair the Network Layer
Scenario
You have been asked to troubleshoot WAN connections for a local telephone company (Telco). The Telco router should communicate with four remote sites, but none of them are working. Use your knowledge of the OSI model and a few general rules to identify and repair the errors in the network.
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Part 1: Diagnose and Repair the Physical Layer
Step 1: Diagnose and repair the cabling.
- Examine the Addressing Table to determine the location of the DCE connections.
- Each serial connection has a DCE and a DTE connection. To determine if each Telco interface is using the correct end of the cable look on the third line of output following the show controllers command.
- Telco# show controllers [interface_type interface_num]
- Reverse any cables that are incorrectly connected.
Note: Cable between Telco and R4 should be reversed and clock rate set on Telco. Serial Cable on R4 should connect to S0/0/1.
Note: In real network settings, the DCE (which sets the clock rate) is typically a CSU/DSU.
Step 2: Diagnose and repair incorrect port connections.
- Examine the Addressing Table to match each router port with the correct Telco port.
- Hold the mouse over each wire to ensure that the wires are connected as specified. If not, correct the connections.
Step 3: Diagnose and repair ports that are shutdown.
- Show a brief interface summary of each router. Ensure that all of the ports that should be working are not administratively down.
- Enable the appropriate ports that are administratively down:
Part 1: Diagnose and Repair the Data Link Layer
Step 1: Examine and set clock rates on DCE equipment.
- All of the DCE cables should be connected to Telco. Show the running configuration of Telco to verify that a clock rate has been set on each interface.
- Set the clock rate of any serial interfaces that requires it:
Step 2: Examine the encapsulation on DCE equipment.
- All of the serial interfaces should be using HDLC as the encapsulation type. Examine the protocol setting of the serial interfaces.
- Telco# show interface [interface_type interface_num]
- Change the encapsulation type to HDLC for any interface that is set otherwise:
Part 3: Diagnose and Repair the Network Layer
Step 1: Verify the IP addressing.
- Show a brief interface summary of each router. Check the IP addresses against the Addressing Table and ensure that they are in the correct subnet with their connecting interface.
- Correct any IP addresses that overlap, or are set to the host or broadcast address:
Step 2: Verify connectivity between all routers.
This tutorial explains basic show commands (such as show ip route, show ip interfaces brief, show version, show flash, show running-config, show startup-config, show controllers, etc.) in Cisco router with examples. Learn how to use show commands in Cisco router to get specific information.
To explain basic router show commands, I will use packet tracer network simulator software. You can use any network simulator software or can use a real Cisco router to follow this guide. There is no difference in output as long as your selected software contains the commands explained in this tutorial.
Create a practice lab as shown in following figure or download this pre-created practice lab and load in packet tracer
If require, you can download the latest as well as earlier version of Packet Tracer from here. Download Packet Tracer
In this practice lab
Device / Interface | Connected To | IP Address |
PC0 | Router0's FastEthernet 0/0 | 10.0.0.2/255.0.0.0 |
Router0's FastEthernet 0/0 | PC0 | 10.0.0.1/255.0.0.0 |
Router0's Serial 0/0/0 | Router1's serial 0/0/0 | 50.0.0.1/255.0.0.0 |
Router1's Serial 0/0/0 | Router0's serial 0/0/0 | 50.0.0.2/255.0.0.0 |
Router1's FastEthernet 0/0 | PC1 | 20.0.0.1/255.0.0.0 |
PC1 Router1's | FastEthernet 0/0 | 20.0.0.2/255.0.0.0 |
- RIP Routing protocol is configured on both routers.
- Clock rate and bandwidth is assigned on Router0’s serial interface 0/0/0.
Above practice lab is only a recommendation to understand the show commands more clearly, it’s not a requirement to follow this tutorial. You can follow this tutorial in a single router or even without router.
Basic Cisco Router Show Commands
Access CLI prompt of router
Use enable command to enter in privilege exec mode. Cisco IOS supports unique context sensitive help features. We can use this features to list all available commands and parameters those are associated with show command.
Email backup pro 2 8. Enter show command with ? ( Question mark ) to list all available commands
If prompt returns with parameters excluding <CR> that means it requires more parameters to complete this command.
If prompt returns with <CR> only as option, that means router does not need any additional parameters to complete this command. You can execute this command in current condition.
Router#show interfaces
This command shows the status and configuration of interfaces. By default it will display all interfaces. But you can limit it to particular interface. To view the detail of specific interface you can use the following command.
Interface S0/0/0 Dce
For example to view the detail of serial 0/0/0 interface on Router0 we will use following command
Output of this command provides several details about interface including its status, encapsulation, interface type, MTU, last input and output packet etc. First line of output shows the status of interface. First up indicates the status of physical layer. Second up refers the data link layer status.
Possible status of physical layer
- UP: - Interface is receiving physical layer signals.
- Down:- Interface is not receiving physical layer signals. This could be happen due to following reasons.
- Cable is unplugged
- You are using wrong cable type.
- Attached device is turned off.
- Administratively down:- Interface is turned off by using shutdown command.
Possible status of data link layer
- UP:- interface is operational.
- Down:- interface is not operational. This could be due to following reasons:-
- Physical layer is down
- Incorrect encapsulation setting
- Incorrect clock rate or bandwidth setting
- Incorrect keepalives setting
Interface status | Description |
UP and UP | Interface is operational |
UP and Down | Check data link layer for possible reasons given above |
Down and Down | Check physical layer for possible reasons given above |
Administratively down and down | Interface is disabled with shutdown command |
- Second line shows the Hardware type and MAC address of interface.
- Third line shows the IP address of interface.
- MTU indicates the Ethernet frame size.
- BW parameter refers to bandwidth link
Router# show ip interface brief
This command provides a quick overview of all interfaces on the router including their IP addresses and status.
Router#show controllers [type slot_# port_#]
This command is used to check the hardware statistic of interface including clock rate and cable status such as cable is attached or not. One end of serial cable is physically DTE, and other end is DCE. If cable is attached, it will display the type of cable.
Router#show flash
This command will display the content of flash memory, used space and available space. By default router stores IOS image file in flash. We can use this command to check the available space in Flash memory while updating / restoring IOS files.
Router#show version
This command will display information about software version of running IOS. It also provides information about configuration setting. It shows current configuration register setting that is used to reset the password of router.
Router#show startup-config
Routers load configuration from NVRAM in startup. This command will display the configuration stored in NVRAM.
Router#show running-config
Router keeps all running configuration in RAM. This command will display the configuration currently running in RAM.
Router#show clock
This command displays current time on router.
Interface S0 0 0 Dce 1
Router#show hosts
This command displays names and addresses of the hosts on the network that you can connect.
Router#show users
Cocktail 11 5 – general maintenance and optimization utility manager. This command displays users currently connected to the router.
Router#show arp
This command displays ARP cache table. ARP table is used to resolve the hardware MAC addresses.
Router#show protocols
This command shows the status of configured layer three protocols on the device.
Router#show history
Router keeps a history of used command. This command will list the used command on that level.
0/0 Equals
Router#show ip route
0/0 Siri
Routers use routing table to take packet forward decision. This command displays routing table.
Interface S0 0 0 Dce Login
Show command supports several other parameters to display command specific information. Due to length of this article we will include them in next articles with their respective topics.