Troubleshoot Ethernet Connectivity
Introduction      Requirements      Verify the Physical Connection      Verify Ethernet Settings           Verify PC Network Settings           Connect to the Cisco Device with HyperTerminal           Verify the Ethernet State on the Cisco Device           Configure the Ethernet Interface on the Cisco Device      Verify the Network Connection      Related Information	Download PDF   Troubleshoot Ethernet Connectivity

Introduction

This document shows you how to troubleshoot connectivity issues that you may encounter when you install and operate your Cisco network device.

Back to Top

Requirements

To perform the steps described in this document, you need to have a console cable.

Back to Top

Verify the Physical Connection

To verify the cable between the Cisco device and your PC, follow these steps:

1. Confirm that you have used a crossover cable to connect the Ethernet port on the PC to the Ethernet port of the Cisco device. For more information about how to identify a crossover cable, refer to Cable Descriptions.

   This example uses a Cisco 800 series router.

   

2. Verify that the Cisco device power switch is in the On ( | ) position and that the power LED on the front panel is lit.

3. Verify that the PC is powered on.

4. Verify that the LINK LED on the Cisco device is lit. If the LINK LED is not lit, verify that the cable between the PC and the Cisco device is connected properly. If possible, replace the cable. Ensure that the LINK LED is illuminated before you proceed to the next section.

Back to Top

Verify Ethernet Settings

To troubleshoot the connection between the Cisco device and your PC, you need to verify the Ethernet settings on each device.

Verify PC Network Settings

To verify that you have the correct network settings on your PC, follow these steps:

1. On the PC, click Start > Run, type cmd, and click OK to start a command prompt.

   Note: If your computer displays an error, enter command instead of cmd.

   Type ipconfig and press Enter to display the IP settings on your PC.

   

2. Verify that your PC has the correct IP address. Your PC's IP address should match the range of the IP address of your Cisco device.

   For example, if your Cisco device has the IP address 192.168.10.1 and subnet mask 255.255.255.0, your PC should have an IP address in the range 192.168.10.2-254 and the same subnet mask. If you need to change your IP address, refer to Configure an IP Address on Your PC.

Connect to the Cisco Device with HyperTerminal

To perform some diagnostic functions on your Cisco device, you need to create a terminal connection. To connect to the Cisco device with HyperTerminal, follow these steps:

1. Connect to the Cisco device with a terminal application. For more information, refer to Create a HyperTerminal Connection.

2. Log in to the Cisco device. The default login is username cisco and password cisco.

3. Type enable and press Enter to use privileged mode.

   Cisco> enable
   Password:
   Cisco#

Verify the Ethernet State on the Cisco Device

You can use the command-line interface (CLI) to verify the state of your Ethernet interface and the current configuration. To verify the interface configuration on the Cisco device, follow these steps:

1. Type show interface FastEthernet0 and press Enter to show the current status of your Ethernet interface.

   Note: The name of your Ethernet interface varies across Cisco devices. Review this table to determine the name of your first Ethernet interface. For example, if your Ethernet interface is named FastEthernet0/0, you need enter to the command show interface FastEthernet0/0. If you have a device with multiple Ethernet interfaces such as a switch, you can enter a higher number as the interface number. For example, the last Ethernet port on a 24 port switch is named FastEthernet0/24.

   Cisco Device Model	First Ethernet Interface
   Catalyst Switch	FastEthernet0/1
   Aironet 1200 Access Point	FastEthernet0 Note: The Aironet BVI1 interface must also be enabled for you to connect to the Ethernet port.
   SOHO Router	Ethernet0
   800 Series Router	Ethernet0
   1760 Router	FastEthernet0/0
   1700 Series Router	FastEthernet0
   1800 Router	FastEthernet0/0
   2600 Series Router	FastEthernet0/0
   2800 Router	FastEthernet0/0
   Cisco PIX	Ethernet1 (inside interface)

   The output shows the state of the Ethernet interface and the IP address assigned to the interface.

   Cisco# show interface FastEthernet0
   FastEthernet0 is up, line protocol is up
     Hardware is PQUICC_FEC, address is 000f.23f5.5d64 (bia 000f.23f5.5d64)
     Description: $ETH-LAN$$ETH-SW-LAUNCH$
     Internet address is 192.168.10.1/24
     MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
   !--- Output truncated.
   
   

2. Compare the first line of output from the Cisco device to the items in this table. The table gives instructions for how to troubleshoot each interface state.

   Interface State	Action
   FastEthernet0 is up, line protocol is up	The status "FastEthernet0 is up" indicates that the interface is properly activated/enabled. The status "line protocol is up" indicates that the interface is properly connected to your PC. If you are unable to connect to the Cisco device, verify that the IP addresses are in the same range. For more information about how to assign an IP address, refer to Configure an IP Address on Your PC.
   FastEthernet0 is administratively down, line protocol is down	The status "FastEthernet0 is administratively down" indicates that the interface is turned off in the Cisco device configuration. To bring the interface up, see Configure the Ethernet Interface on the Cisco Device.
   FastEthernet0 is up, line protocol is down	The status "FastEthernet0 is up" indicates that the interface is properly activated/enabled but the interface cannot communicate with the PC. Check the cable between the Cisco device and the PC to ensure that you are using a crossover cable, and verify the status of the PC. For more information about how to identify a cable, refer to Cable Descriptions.

Configure the Ethernet Interface on the Cisco Device

If your Cisco device Ethernet interface does not have an IP address or is shut down, you need to configure your interface. To configure the Cisco device Ethernet interface, follow these steps:

1. At the Cisco# prompt, type configure terminal and press Enter.

   Cisco# configure terminal
   Enter the configuration commands, one per line. End with CNTL/Z.
   Cisco(config)#

2. Type interface fastethernet0 and press Enter.

   Note: The name of your Ethernet interface varies across Cisco devices. Review this table to determine the name of your first Ethernet interface. For example, if your Ethernet interface is named FastEthernet0/0, you need enter to the command interface FastEthernet0/0. If you have a device with multiple Ethernet interfaces such as a switch, you can enter a higher number as the interface number. For example, the last Ethernet port on a 24 port switch is named FastEthernet0/24.

   Cisco Device Model	First Ethernet Interface
   Catalyst Switch	FastEthernet0/1
   Aironet 1200 Access Point	FastEthernet0 Note: In order to connect, you must configure an IP address on both the Ethernet interface and the BVI1 interface. The BVI1 interface must match the IP address that you use to connect to the access point.
   SOHO Router	Ethernet0
   800 Series Router	Ethernet0
   1760 Router	FastEthernet0/0
   1700 Series Router	FastEthernet0
   1800 Router	FastEthernet0/0
   2600 Series Router	FastEthernet0/0
   2800 Router	FastEthernet0/0
   Cisco PIX	Ethernet1 (inside interface)

   Cisco(config)# interface fastethernet0
   Cisco(config-if)#

3. Type no shutdown and press Enter.

   Cisco(config-if)# no shutdown
   

   Note: If you have a PIX Security Appliance, type interface ethernet1 100full and press Enter.

4. Type ip address ip-address subnet-mask to assign an IP address to the Cisco device. If you need to determine the correct IP address for the Cisco device, refer to the Site Survey.

5. Type end and press Enter.

   Cisco(config-if)# end
   Cisco#

   Note: If you have a PIX Security Appliance, type quit and press Enter.

6. Type write memory and press Enter to save your configuration.

   Cisco# write memory
   

7. See Verify the Ethernet State on the Cisco Device to confirm that your Ethernet interface is now active.

Back to Top

Verify the Network Connection

A ping test allows you to test the connection between your PC and Cisco device. To verify a connection with a ping test, follow these steps:

1. On the PC, click Start > Run, type cmd or command, and click OK to start a command prompt.

2. Type ping cisco-device-ip-address and press Enter.

   

3. Check the command output to determine whether or not the ping test was successful.

   • If the ping is successful, the DOS prompt displays output similar to this example.

     Pinging 192.168.10.1 with 32 bytes of data:
     
     Reply from 192.168.10.1: bytes=32 time<10ms TTL=128
     Reply from 192.168.10.1: bytes=32 time<10ms TTL=128
     Reply from 192.168.10.1: bytes=32 time<10ms TTL=128
     Reply from 192.168.10.1: bytes=32 time<10ms TTL=128
     
     Ping statistics for 192.168.10.1:
         Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
     Approximate round trip times in milli-seconds:
         Minimum = 0ms, Maximum =  0ms, Average =  0ms

   • If the ping is not not successful, the DOS prompt displays output similar to this example.

     Pinging 192.168.10.1 with 32 bytes of data:
     
     Request timed out.
     Request timed out.
     Request timed out.
     Request timed out.
     
     Ping statistics for 192.168.10.1:
         Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
     Approximate round trip times in milli-seconds:
         Minimum = 0ms, Maximum =  0ms, Average =  0ms

     If you are unable to perform a ping test successfully, see Verify the Physical Connection.

Back to Top

Related Information

• Cable Descriptions
• Configure an IP Address on Your PC
• Create a HyperTerminal Connection