The Packet Tracer Lab Manual

How this manual works

Every network — up to the whole Internet — is built from one idea: a sender moves a message to a receiver over a medium, both obeying a protocol. In Packet Tracer we’ll place two PCs, join them with a cable, give them addresses, and prove they can talk with a ping.

Why it matters. Those two PCs are the sender and receiver; the cable is the medium. The link lights start red — they’ll go green once both ends have a matching configuration.

What it does. Each PC now has a Layer-3 IP address on the same network (both start 192.168.1 with a /24 mask), so they consider each other “local” and can talk directly.

Why it matters. Without addresses the two PCs are connected but mute — exactly the “connected but not communicating” idea. The mask (255.255.255.0) is what tells each PC the other is on the same network.

ping 192.168.1.2

What it does. ping sends four small test messages (ICMP echo requests) to PC1 and waits for replies. It’s the “are you there?” of networking.

Pinging 192.168.1.2 with 32 bytes of data:
Reply from 192.168.1.2: bytes=32 time<1ms TTL=128
Reply from 192.168.1.2: bytes=32 time<1ms TTL=128
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)

Why it matters. Four replies = a full round-trip conversation. You just moved a message from a sender (PC0) to a receiver (PC1) over a medium (the cable) using a protocol (ICMP over IP). That’s the whole of Chapter 1, on the canvas. (First ping may show one “Request timed out” while ARP resolves — Chapter 3 explains why.)

Add a switch and you have a tiny LAN. Every host has two addresses — a hardware MAC and a logical IP — and every message gets encapsulated: wrapped in an IP packet, then an Ethernet frame. Packet Tracer’s Simulation mode is your built-in Wireshark for watching those layers.

Why it matters. The switch is a Layer-2 device: it forwards frames by MAC address, learning which MAC lives on which port. It lets many hosts share the LAN instead of a single cable.

ipconfig /all

What it does. Prints this PC’s full addressing. Look for Physical Address (the MAC — burned into the “card”) and IPv4 Address (the IP — assigned by you).

Physical Address...: 0060.7C2A.9B11
IPv4 Address.......: 192.168.1.1
Subnet Mask........: 255.255.255.0

Why it matters. The MAC (Layer 2) identifies the card on the local link; the IP (Layer 3) identifies the host on the network. Chapter 3 shows how the two get glued together.

What it does. The PDU window shows the OSI Model tab (Layers 1–7) and the Outbound PDU tab (the real header bytes) for that one packet.

Layer 2: Ethernet II  Src/Dst MAC
Layer 3: IP           Src/Dst IP
Layer 4/…: ICMP echo request

Why it matters. Read it outside-in: an Ethernet frame (MAC → MAC) carrying an IP packet (IP → IP) carrying an ICMP message. That nesting is encapsulation — the OSI layers, made of real bytes you can click through.

enable
show mac address-table

Vlan   Mac Address       Type      Ports
1      0060.7c2a.9b11    DYNAMIC   Fa0/1
1      0002.16aa.bb22    DYNAMIC   Fa0/2

Why it matters. The switch has learned which MAC is on which port, so it can forward frames only where they need to go. This table is Layer-2 forwarding in action.

A switch forwards by MAC, but you address hosts by IP. ARP bridges the two: “who has 192.168.1.1? tell me your MAC.” We add a router as the LAN’s default gateway — the door off the LAN — and watch ARP resolve it in Simulation mode. Golden rule: IP is end-to-end, MAC is hop-to-hop.

enable
configure terminal
 hostname R1
 interface gigabitEthernet0/0
  ip address 192.168.1.254 255.255.255.0
  no shutdown
 exit
end

What it does. configure terminal enters config mode; interface g0/0 selects the LAN port; ip address gives it the gateway IP; no shutdown turns the port on. Now set both PCs’ Default Gateway to 192.168.1.254 in Desktop ▸ IP Configuration.

Why it matters. The gateway is the router interface a host uses to reach any network that isn’t its own. Almost everything a PC does eventually goes through it.

1. ARP Request  (broadcast)  "who has 192.168.1.254?"
2. ARP Reply    (unicast)    "192.168.1.254 is at 00E0.A3..."
3. ICMP echo   (now the ping can actually be sent)

Why it matters. A host can’t build the Ethernet frame until it knows the destination MAC. ARP is that lookup: a broadcast question, a unicast answer. Only then does the ping go out.

arp -a

Internet Address      Physical Address      Type
192.168.1.254         00e0.a3bb.cc01        dynamic

Why it matters. The PC caches the mapping it just learned, so it doesn’t ARP again for a while. Notice it keeps an entry for the gateway — because that’s the door it uses most. When you ping a remote address, the frame’s destination MAC is the gateway’s (hop-to-hop), while the IP is the far server’s (end-to-end).

Give the router a second interface and a second LAN, and packets now leave their home network. A router only forwards between networks it knows about — we’ll configure both interfaces, read the router’s routing table, and trace a packet across the hop.

configure terminal
 interface gigabitEthernet0/1
  ip address 10.0.0.1 255.255.255.0
  no shutdown
 end
copy running-config startup-config

What it does. R1 now has one foot in each network: 192.168.1.254 on g0/0 and 10.0.0.1 on g0/1. copy running-config startup-config saves the config so it survives a reload.

show ip interface brief
show ip route

Interface              IP-Address      Status  Protocol
GigabitEthernet0/0     192.168.1.254   up      up
GigabitEthernet0/1     10.0.0.1        up      up

C    192.168.1.0/24 is directly connected, GigabitEthernet0/0
C    10.0.0.0/24 is directly connected, GigabitEthernet0/1

Why it matters. The two C (connected) routes are what let R1 forward between the LANs. A router only sends traffic to networks in this table — Chapter 9 is all about filling it with routes to networks the router isn’t directly on.

ping 10.0.0.10
tracert 10.0.0.10

Reply from 10.0.0.10: bytes=32 time<1ms TTL=127
Tracing route to 10.0.0.10 ...
  1   1 ms   192.168.1.254   <- the router R1 (one hop)
  2   0 ms   10.0.0.10        <- destination PC2

Why it matters. PC0 and PC2 are on different networks, so the packet had to cross R1 — and tracert shows that single hop. The TTL dropped from 128 to 127 as the router forwarded it: that’s the IP header field the whole Internet uses to stop loops.

Connect R1 to an ISP router and a public server. Two ideas: ICMP is the network’s error-and-echo voice (it powers ping and tracert), and NAT/PAT lets a whole private LAN share one public address. You’ll configure PAT and watch a private address become public.

configure terminal
 interface gigabitEthernet0/2
  ip address 203.0.113.2 255.255.255.252
  no shutdown
 exit
 ip route 0.0.0.0 0.0.0.0 203.0.113.1
 end

What it does. Gives R1 a public WAN address and a default route (0.0.0.0 0.0.0.0) that says “anything I don’t have a specific route for, send to the ISP at 203.0.113.1.” On R-ISP, give g0/0 203.0.113.1/30 and g0/1 198.51.100.1/24.

configure terminal
 interface gigabitEthernet0/0
  ip nat inside
 interface gigabitEthernet0/1
  ip nat inside
 interface gigabitEthernet0/2
  ip nat outside
 exit
 access-list 1 permit 192.168.1.0 0.0.0.255
 access-list 1 permit 10.0.0.0 0.0.0.255
 ip nat inside source list 1 interface gigabitEthernet0/2 overload
 end
copy running-config startup-config

What it does. ip nat inside/outside marks the private and public sides. The access-list says “these private networks get translated,” and overload makes it PAT — every inside host shares the one public interface address, told apart by port numbers.

ping 198.51.100.10

show ip nat translations

Pro  Inside global       Inside local      Outside...
icmp 203.0.113.2:1     192.168.1.1:1     198.51.100.10:1

Why it matters. The inside local is PC0’s private address; the inside global is the single public address the world sees. That translation is why thousands of networks can all reuse 192.168.x.x — and it’s ICMP (the ping) that proved the path end-to-end.

One flat /24 wastes addresses and mixes everyone together. Subnetting borrows host bits to make smaller networks; VLSM sizes each to its real host count. We’ll apply a plan with router-on-a-stick — one physical link carrying several subnets on subinterfaces — the exact technique behind the NSSA-241 capstone.

Why it matters. Each subnet is sized to its host count with almost no waste. The next subnet always starts one block size after the last (0 → 64 → 96 → 112) — that “add the block size” move is the whole skill.

enable
configure terminal
 vlan 10
  name STUDENTS
 vlan 20
  name FACULTY
 interface fastEthernet0/1
  switchport mode access
  switchport access vlan 10
 interface fastEthernet0/3
  switchport mode trunk
 end

What it does. A VLAN is a separate Layer-2 network on the same switch. Access ports belong to one VLAN (PC0 → VLAN 10); the port to the router is a trunk, which carries all VLANs tagged with their number (802.1Q).

configure terminal
 interface gigabitEthernet0/0
  no ip address
  no shutdown
 interface gigabitEthernet0/0.10
  encapsulation dot1Q 10
  ip address 192.168.1.1 255.255.255.192
  ip nat inside
 interface gigabitEthernet0/0.20
  encapsulation dot1Q 20
  ip address 192.168.1.65 255.255.255.224
  ip nat inside
 end
copy running-config startup-config

What it does. One physical port (g0/0) is split into subinterfaces, each tagged to a VLAN with encapsulation dot1Q and given that subnet’s gateway address and mask. Notice the masks: /26 = 255.255.255.192, /27 = 255.255.255.224.

show ip route

C   192.168.1.0/26   is directly connected, GigabitEthernet0/0.10
C   192.168.1.64/27  is directly connected, GigabitEthernet0/0.20

Why it matters. The router now routes between the department subnets, and each VLAN’s broadcast traffic stays contained. A Students PC in .0/26 and a Faculty PC in .64/27 can only reach each other through R1 — segmentation, done with subnet maths.

Two helpers make the network usable. DHCP hands a joining PC its address automatically (the DORA exchange), and DNS turns names into IP addresses. We’ll configure a DHCP pool on the router and a DNS server, then watch a PC pick up an address and resolve a name.

configure terminal
 ip dhcp excluded-address 192.168.1.1 192.168.1.5
 ip dhcp pool STUDENTS
  network 192.168.1.0 255.255.255.192
  default-router 192.168.1.1
  dns-server 192.168.1.113
 end

What it does. ip dhcp pool creates a lease pool for the Students /26. network is the range to hand out, default-router and dns-server are given to each client, and excluded-address reserves the low addresses (gateway, servers) from being leased.

Why it matters. That one click triggered the whole DORA handshake — Discover, Offer, Request, Ack — over UDP ports 67/68. No human typed the address; the router leased it. Switch to Simulation mode and repeat to watch the four DHCP packets fly.

Why it matters. This server is now authoritative for www.lab.local — it holds the name→IP mapping, exactly like the authoritative servers in the DNS hierarchy from the slides.

nslookup www.lab.local

Server:  192.168.1.113
Name:    www.lab.local
Address: 192.168.1.113

Why it matters. The PC asked the DNS server “what IP is this name?” and got an answer — the whole job of DNS. Open PC0 ▸ Desktop ▸ Web Browser and visit http://www.lab.local to see it work end-to-end.

The network layer got the packet to the right host; the transport layer gets it to the right application — using port numbers. TCP sets up a reliable session with a three-way handshake; UDP just fires and forgets. Packet Tracer’s Simulation mode lets us watch both, and read the port numbers in the PDU.

Why it matters. A server is just a program “listening” on a port. HTTP lives on 80, HTTPS on 443, DNS on 53, DHCP on 67/68. The port is how one machine runs many services without confusion.

1. PC0 → Server  TCP  SYN       (src port 1025 → dst port 80)
2. Server → PC0  TCP  SYN, ACK
3. PC0 → Server  TCP  ACK       (now the HTTP GET follows)

Why it matters. Before a single byte of the web page moves, TCP does SYN → SYN-ACK → ACK. It proves the server is there, the port is open, and both sides agree to start — the foundation of reliable delivery. Note the socket: your ephemeral port (1025) ↔ the server’s well-known port (80).

1. PC0 → Server  DNS query   (UDP src 1026 → dst 53)
2. Server → PC0  DNS response

Why it matters. Compare with step 2: no SYN, no ACK, no teardown. UDP just sends the datagram and hopes. That’s why DNS, DHCP and live video use it — speed over guarantees.

Grow past one router. Routers only forward to networks in their table — a static route is one you type by hand; a routing protocol (RIP, OSPF) lets routers learn each other’s networks automatically. We add a second router and do both, reading the routing table each time.

configure terminal
 ip route 172.16.0.0 255.255.255.0 10.10.10.2
 end
show ip route

S    172.16.0.0/24 [1/0] via 10.10.10.2

What it does. ip route <network> <mask> <next-hop> tells R1 “to reach 172.16.0.0/24, send to R2 at 10.10.10.2.” You’d also add the reverse route on R2.

configure terminal
 router ospf 1
  network 192.168.1.0 0.0.0.63 area 0
  network 10.10.10.0 0.0.0.3 area 0
 end

What it does. router ospf 1 starts the OSPF link-state protocol; each network line tells OSPF which of its own interfaces to advertise (the wildcard mask 0.0.0.3 = a /30). Configure the matching networks on R2 and the two routers become neighbours and swap routes.

show ip ospf neighbor
show ip route

Neighbor ID   State     Address       Interface
10.10.10.2    FULL/  -  10.10.10.2    GigabitEthernet0/2

O   172.16.0.0/24 [110/2] via 10.10.10.2   <- learned by OSPF

Why it matters. The O route was learned automatically — you never typed it. If a link fails, OSPF recomputes and reroutes on its own (that’s the “link-state / Dijkstra” idea from the slides). RIP (router rip → version 2 → network) does the same job the distance-vector way, with routes marked R.

The finale: give every device a second, much bigger address. IPv6 swaps 32-bit addresses for 128-bit ones and lets a router hand out prefixes automatically (SLAAC). We’ll enable IPv6 routing, address an interface, let a PC auto-configure, and ping over IPv6 — dual-stack, running right beside IPv4.

configure terminal
 ipv6 unicast-routing
 interface gigabitEthernet0/0
  ipv6 address 2001:DB8:ACAD:1::1/64
  ipv6 address FE80::1 link-local
  no shutdown
 end

What it does. ipv6 unicast-routing turns on IPv6 forwarding globally. The interface gets a global address (2001:DB8:...::1/64, routable) and a link-local (FE80::1, for on-link chatter only). The /64 is the standard LAN prefix.

Why it matters. Every IPv6 interface has two addresses at once: a link-local for local use and a global for the Internet. SLAAC means hosts can address themselves from the router’s /64 — a headline IPv6 feature.

show ipv6 interface brief
show ipv6 route

ping 2001:DB8:ACAD:1::1

GigabitEthernet0/0   [up/up]
    FE80::1
    2001:DB8:ACAD:1::1
...
Reply from 2001:DB8:ACAD:1::1: bytes=32 time<1ms (IPv6 works!)

Why it matters. Your PC just reached the router over IPv6, while IPv4 still works too — that’s dual-stack. You’ve now built and configured every layer of a real network, in both address families, entirely in Packet Tracer.