Data Communication & Networks · 2025–26

DCN Practical Exam Kit

Ten selected experiments · aim, procedure, runnable code, illustrated output and result

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Experiment 8 — ICMP, ARP, DHCP and NAT

Manual pages: 74–81 | Tools: Wireshark + Cisco Packet Tracer

AIM

To analyze ICMP/ARP packets using Wireshark and configure DHCP and NAT in Cisco Packet Tracer.

PART A — WIRESHARK PROCEDURE

  1. Open Wireshark; capture traffic on an authorized active network interface.
  2. In Windows Command Prompt: ping 8.8.8.8. Filter Wireshark with icmp.
  3. Select Echo Request / Echo Reply. Examine IP source/destination, ICMP type (8 request, 0 reply), TTL and sequence.
  4. To observe ARP for your own gateway, first start capture and ping your gateway (example ping 192.168.1.1). If its MAC is already cached, clear that entry if permitted (manual uses arp -d *, which may require administrator rights), then ping again. Apply arp filter.
  5. Note ARP sender/target MAC + IP and Request/Reply; stop and save a .pcapng capture.

PART B — DHCP PROCEDURE

  1. New Packet Tracer project: PC0, PC1 → Switch0 → Router0 G0/0.
  2. Router0 CLI: enter DHCP_Router.cli.
  3. Both PCs → Desktop → IP Configuration → DHCP; choose DHCP rather than Static.
  4. PC0 Command Prompt: ipconfig. Observe assigned address 192.168.1.x, mask /24 and gateway 192.168.1.1.
  5. Router0 CLI: show ip dhcp binding to see leased addresses. Test ping 192.168.1.1.

PART C — NAT/PAT PROCEDURE (separate topology)

  1. New Packet Tracer project: PC0/PC1 → Switch0 → Router0 (LAN G0/0) ↔ (G0/1) Router1 (outside G0/0).
  2. Assign PC0 192.168.1.10/24 and PC1 192.168.1.11/24, gateway 192.168.1.1. LAN = 192.168.1.0/24, WAN link = 200.1.1.0/30.
  3. Router0 CLI: NAT_Router0_Ethernet.cli. Router1 CLI: NAT_Router1_Simulated_Outside.cli.
  4. The second router has loopback 8.8.8.8 representing a test destination; this does not make the real Internet reachable. This is a complete local simulation to replace the manual's assumed external network. The manual uses serial S0/0/0, but the included scripts assume Ethernet G0/1 on Router0.
  5. On PC0 run ping 8.8.8.8 then on Router0 show ip nat translations / show ip nat statistics. Translations may be transient after ICMP exits; retry ping while checking.

EXPECTED OUTPUT

ICMP: Echo Request Type 8; Echo Reply Type 0
ARP: Request to resolve IPv4 to MAC; Reply provides MAC
DHCP: 192.168.1.x / 255.255.255.0 / gateway 192.168.1.1
NAT: inside local 192.168.1.10 -> inside global 200.1.1.1

RESULT

Thus, ICMP/ARP were analyzed using Wireshark; DHCP addressing and NAT overload were configured and tested in Cisco Packet Tracer.

VIVA