Free Cisco Packet Tracer Activity Network Discovery

Posted by: admin  :  Category: Lab Scenarios, Packet Tracer, Routing, Switching

So far our previous labs have been dedicated to configuring and troubleshooting routing and switching. This lab is a little different but is still an essential part of the network engineer’s knowledge base. In this lab we will use tools like ping, and tracert along with show commands like show ip arp, show mac-address-table and show cdp neighbors to explore and document an existing network using nothing but a telnet session on a host PC. 

Learning Objectives:

  • Learn how to find the physical connection of a device using an IP address as the starting point.
  • Learn to use telnet to connect from device to device.
  • Learn to find the IP address of a host device.
  • Learn to get the physical address using the IP address.
  • Learn to use and understand ARP.
  • Learn to use and understand mac-address-tables.
  • Learn to use and understand CDP.
  • Learn to use and interpret the show interface command.


You are a network consultant and your services have been contracted to document an existing network. You have been provided a PC connected to the network along with the console password of “sanfran” and the enable password of “cisco” which should provide you with full access to all routers and switches. No one knows much about the network configuration but they do have a list of host computers and servers. There is a DNS server in place and is believed to be running and up to date. The network is spread over three different sites and it is not practical to travel to these sites so you will need you knowledge to explore the network remotely via telnet.

Before we start let’s review some of protocols and commands we might use to complete this project:

DNS Host Name:
A hostname is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication such as the World Wide Web, or a Local Area Network (LAN). Hostnames may be simple names consisting of a single word or phrase, or they may have appended a domain name, which is a name in a Domain Name System (DNS), separated from the host specific label by a period (dot). In the latter form, the hostname is also called a domain name. If the domain name is completely specified including a top-level domain of the Internet, then the hostname is said to be a fully qualified domain name (FQDN).

Hostnames that include DNS domains are often stored in the Domain Name System together with the IP addresses of the host they represent for the purpose of mapping the hostname to an address, or the reverse process.

IP Address:
An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer, or Server) participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: “A name indicates what we seek. An address indicates where it is. A route indicates how to get there.

MAC Address:
A Media Access Control address (MAC address) is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet. Logically, MAC addresses are used in the Media Access Control protocol sub-layer of the OSI reference model.

MAC addresses are most often assigned by the manufacturer of a network interface card (NIC) and are stored in its hardware, the card’s read-only memory, or some other firmware mechanism. If assigned by the manufacturer, a MAC address usually encodes the manufacturer’s registered identification number and may be referred to as the burned-in address. It may also be known as an Ethernet hardware address (EHA), hardware address or physical address. A network device may have multiple NICs and will then have one unique MAC address per NIC.

Address Resolution Protocol (ARP) is a telecommunications protocol used for resolution of network layer addresses into link layer addresses, a critical function in multiple-access networks.

Tracert or Traceroute:
Tracert or traceroute is a computer network diagnostic tool for displaying the route (path) and measuring transit delays of packets across an Internet Protocol (IP) network.

Show ip arp:
To display the Address Resolution Protocol (ARP) cache, where Serial Line Internet Protocol (SLIP) addresses appear as permanent ARP table entries, use the show ip arp EXEC command.

Usage Guidelines:
ARP establishes correspondences between network addresses (an IP address, for example) and LAN hardware addresses (Ethernet addresses). A record of each correspondence is kept in a cache for a predetermined amount of time and then discarded.
The following is sample output from the show ip arp command:

Router# show ip arp
Protocol  Address Age(min)  Hardware Addr  Type   Interface
Internet 9 0000.0c59.f892 ARPA   Ethernet0/0
Internet 8 0000.0c07.ac00 ARPA   Ethernet0/0
Internet – 0000.0c63.1300 ARPA   Ethernet0/0
Internet 9 0000.0c36.6965 ARPA   Ethernet0/0
Internet – 0000.0c63.1300 ARPA   Ethernet0/0

Show mac-address-table:
Use the show mac-address-table user EXEC command to display the MAC address table.

show mac-address-table [aging-time | count | dynamic | static] [address hw-addr]
[interface interface-id] [vlan vlan-id] [ | {begin | exclude | include} expression]

Usage Guidelines
This command displays the MAC address table for the switch. Specific views can be defined by using the optional keywords and values. If more than one optional keyword is used, all of the conditions must be true in order for that entry to appear.

Expressions are case sensitive. For example, if you enter | exclude output, the lines that contain output do not appear, but the lines that contain Output appear.

This is an example of output from the show mac-address-table command:

Switch> show mac-address-table
Dynamic Addresses Count:               9
Secure Addresses (User-defined) Count: 0
Static Addresses (User-defined) Count: 0
System Self Addresses Count:           41
Total MAC addresses:                   50
Non-static Address Table:
Destination Address  Address Type  VLAN  Destination Port
——————-  ————  —-  ——————–
0010.0de0.e289       Dynamic          1  FastEthernet0/1
0010.7b00.1540       Dynamic          2  FastEthernet0/5
0010.7b00.1545       Dynamic          2  FastEthernet0/5
0060.5cf4.0076       Dynamic          1  FastEthernet0/1
0060.5cf4.0077       Dynamic          1  FastEthernet0/1
0060.5cf4.1315       Dynamic          1  FastEthernet0/1
0060.70cb.f301       Dynamic          1  FastEthernet0/1
00e0.1e42.9978       Dynamic          1  FastEthernet0/1
00e0.1e9f.3900       Dynamic          1  FastEthernet0/1

Show cdp neighbors:
To display detailed information about neighboring devices discovered using Cisco Discovery Protocol (CDP), use the show cdp neighbors privileged EXEC command.

show cdp neighbors [type number] [detail]

The following is sample output for the show cdp neighbors command:

Router#show cdp neighbors
Capability Codes: R – Router, T – Trans Bridge, B – Source Route Bridge
                  S – Switch, H – Host, I – IGMP, r – Repeater
Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
lab-7206         Eth 0              157          R        7206VXR   Fas 0/0/0
lab-as5300-1     Eth 0              163          R        AS5300    Fas 0
lab-as5300-2     Eth 0              159          R        AS5300    Eth 0
lab-as5300-3     Eth 0              122          R        AS5300    Eth 0
lab-as5300-4     Eth 0              132          R        AS5300    Fas 0/0
lab-3621         Eth 0              140         R S       3631-telcoFas 0/0
008024 2758E0    Eth 0              132          T        CAT3000   ½

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3 Responses to “Free Cisco Packet Tracer Activity Network Discovery”

  1. Lisa Gontarski Says:

    Can you please email me or send me a download link to your first CCNA labs? I am not ready for the ultimate CCNA. When I click on CCNA labs, the first line says “So far our previous labs have been dedicated to configuring and troubleshooting routing and switching”, and, I don’t see what link i would click on to download the actual beginner CCNA labs.


  2. admin Says:

    I would suggest you check out my other site the labs there are all CCNA and use Packet Tracer.

  3. spartacus Says:

    thank you very well !!!

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