Verify network status and switch operation using basic utilities

Exam: 200-120 - CCNA Cisco Certified Network Associate CCNA (803)

Once you have configured your network with switches and routers, you may need to verify and troubleshoot your network. Some of the commands that you can use to verify and troubleshot your network arediscussed in this chapter. The commands discussed in the chapter may be used from both a PC and a Cisco router. They may do the same thing but their implementation is different.

Packet InterNet Groper (Ping)

The ping command allows you to verify the connectivity of your PC to the remote hosts. It is a very good command to troubleshoot your network for the connectivity of devices on your network. However, if you need to find out the connectivity of your computer to a different subnet, you need to specify the route to the subnet or configure the router between your subnet and the other subnet to which you want to connect.

The Ping command uses ICMP (Internet Control Message Protocol) echo request and ICMP echo replies query messages to find out whether the remote host is active or not. It also allows you to find out theminimum, average, and maximum time to reach a host and return back.

The ping command works by first sending an echo request to a host. The Ping then waits till it gets a reply from the host. If the ping is able to get to the destination and is able to get an echo reply from the host, the Ping is successful.

The ping command can be executed in normal and privileged mode but cannot be executed in configuration mode. The command returns the following types of output:

  • Normal response: host is alive message is returned with 1 to 10 seconds.
  • Unknown host: ping displays Unknown host message when the host does not exist.
  • Destination unreachable: the default gateway cannot reach the specified network
  • Destination does not respond: ping displays No Answer message.
  • Network or host unreachable:the Network or host unreachable message is displayed when there is no entry of the host in the route table of the host network.

This example shows how to ping a remote host from normal executive mode:

Switch# ping host1

host1is alive

Switch>ping 172.168.10.3

172.168.10.3 is alive

Switch#

In exec mode, the Ping command returns the number of packets, the packet size, and the timeout period as output:

Traceroute

The traceroute command allows you to discover the path or the list of routers taken by a device to reach the network destination. As the name suggests, the traceroute command traces the path that a network packet takes to reach a destination. The traceroute command also allows you to find out the places where the routing has broken down by displaying TTL time-outs and ICMP error messages.

The command cannot be executed from the DOS prompt. The following example displays the hops that the network packet has taken to reach the destination by using the traceroute command:

Todd#trace r1

Typeescape sequence to abort.

Tracing the route to r1.test.com (172.168.10.2)

1 r1.test.com (172.168.10.2) 16 msec * 16 msec

The above example shows that the packet went through a single hop to reach the destination.

Telnet

The telnet command allows you to access the command-line interface (CLI) of the switch and to access other devices on the network using the switch. You need to configure a telnet session to use it by setting up the IP address and settingup the default gateway on the switch.

You can have multiple telnet sessions. The maximum limit of telnet sessions however is 8 simultaneous sessions. The following command opens a Telnet session to a remote host.

Switch#telnethost[port]

This example shows how to establish a Telnet connection from the switch to the remote host named PC1:

Switch# telnet PC1

Trying 172.168.10.3...

Connected to PC1

Escape character is '^]'.

SSH

Just like telnet, the SSH (secure shell) is also used to build a connection to a router, a switch or other networking devices for network management. However, the SSH command is a secure option to use as compared to telnet because telnet does not encrypt its connections whereas SSH encrypts its connections. A hacker can easily capture the network packets from a telnet session but cannot capture packets from an SSH session.

SSH uses digital certificates, in a Public/Private Key Cryptography to authenticate client and server computers.

Just like telnet, you need to configure SSH on your router with hostname, domain name and generate a certificate to encrypt SSH packets.

ARP

The ARP command allows you to add an entry in the Address Resolution Protocol (ARP) cache, which is used by a software application to translate 32-bit IP addresses into 48-bit hardware addresses.

The ARP command allows you to create IP-to-MAC address mappings. To add a permanent entry in the ARP cache, you need to execute the command in global configuration mode and to remove an entry from the cache you need to use the No form of this command.

arp[vrfvrf-name]ip-addresshardware-addressencapsulation-type[alias]

noarp[vrfvrf-name]ip-addresshardware-addressencapsulation-type[alias]

Where:/p>

vrf: specifies VPN routing and forwarding instance. This is an optional parameter for the command.

Vrf name: specifies the VRF instance that identifies a VPN. This is an optional parameter for the command.

Ip-address : IP address (Ipv4 address) for which a permanent entry is to be added to the ARP cache

hardware-address : Hardware (data link layer) address that the IPv4 address is linked to.

Encapsulation-type :the encapsulation types are:arpa, srp, srpa, srpb.

For Ethernet interfaces, the arpa encapsulation is used typically.

The following example shows a static ARP entry for a typical Ethernet host:

RP/0/RP0/CPU0:router# configure

RP/0/RP0/CPU0:router(config)# arp 192.168.17.19 0800.0900.1834 arpa

Iconfig

The ipconfig command allows you to view the current IP settings of your NIC on your PC or for your router’s LAN/WAN interfaces. The output of the ipconfig command displays the IP Address, Subnet Mask, Default Gateway, and (on a PC), even the DNS Servers.

Show and debug commands

The show and debug commands have multiple options and are available for many features and functions within CiscoIOS software. To show command is used to verify the MST (Multiple Spanning Tree) configuration. Some examples of show commands are show interface, show buffers, showsection, and showflash.

The debug command allows you to troubleshoot your network with the extensive output that the command generates. Someexamples of debugcommands aredebug all,debug aaa accounting, anddebug mpls packets. You need a telnet session to use debug commands. You can turn off the debug command by using undebug all command.

Example Question

Which of the following commands would you use to display all the current IP settings on your switch?

  • ping
  • SSH
  • arp
  • ipconfig

Answer: D

The ipconfig command allows you to view the current IP settings of your NIC on your PC or for your router’s LAN/WAN interfaces.

Related IT Guides

  1. Configure and verify ACLs in a network environment
  2. Configure and verify an ACLs to limit telnet and SSH access to the router
  3. Configure and verify DHCP (IOS Router)
  4. Configure and verify initial switch configuration including remote access management
  5. Configure and verify interVLAN routing (Router on a stick)
  6. Configure and verify VLANs
  7. Describe the types, features, and applications of ACLs
  8. Identify and correct common network problems
  9. Select the appropriate media, cables, ports, and connectors to connect switches to other network devices and hosts
  10. Select the Components Required to Meet a Network Specification

Close 100% Pass Guarantee or Your Money Back

How to Claim the Refund / Exchange?

In case of failure your money is fully secure by BrainDumps Guarantee Policy. Before claiming the guarantee all downloaded products must be deleted and all copies of BrainDumps Products must be destroyed.


Under What Conditions I can Claim the Guarantee?

Full Refund is valid for any BrainDumps Testing Engine Purchase where user fails the corresponding exam within 30 days from the date of purchase of Exam. Product Exchange is valid for customers who claim guarantee within 90 days from date of purchase. Customer can contact BrainDumps to claim this guarantee and get full refund at billing@braindumps.com. Exam failures that occur before the purchasing date are not qualified for claiming guarantee. The refund request should be submitted within 7 days after exam failure.


The money-back-guarantee is not applicable on following cases:

  1. Failure within 7 days after the purchase date. BrainDumps highly recommends the candidates a study time of 7 days to prepare for the exam with BrainDumps study material, any failures cases within 7 days of purchase are rejected because in-sufficient study of BrainDumps materials.
  2. Wrong purchase. BrainDumps will not entertain any claims once the incorrect product is Downloaded and Installed.
  3. Free exam. (No matter failed or wrong choice)
  4. Expired order(s). (Out of 90 days from the purchase date)
  5. Retired exam. (For customers who use our current product to attend the exam which is already retired).
  6. Audio Exams, Hard Copies and Labs Preparations are not covered by Guarantee and no claim can be made against them.
  7. Products that are given for free.
  8. Different names. (Candidate's name is different from payer's name).
  9. The refund option is not valid for Bundles and guarantee can thus not be claimed on Bundle purchases.
  10. Guarantee Policy is not applicable to Admission Tests / Courses, CISSP, EMC, HP, Microsoft, PMI, SAP and SSCP exams as braindumps.com provides only the practice questions for these.
  11. Outdated Exam Products.
Close
Autumn Sale! Get 30% Discount for All Exams!

This is a ONE TIME OFFER. You will never see this Again

Instant Discount
Braindumps Testing Engine

30% OFF

Enter Your Email Address to Receive Your 30% OFF Discount Code Plus... Our Exclusive Weekly Deals

A confirmation link will be sent to this email address to verify your login.


* We value your privacy. We will not rent or sell your email address.
Close
Your 30% Discount on Your Purchase

Save 30%. Today on all IT exams. Instant Download

Braindumps Testing Engine

Use the following Discount Code during the checkout and get 30% discount on all your purchases:

Promo30Sept17

Start Shopping