00
Make an IP address explain itself
Assign two documentation addresses, read the connected route and inspect the actual IPv4 header.
Tool
Use the Subnet Calculator to predict network and host portions.
Kernel
Read address, prefix and connected route with iproute2.
PCAP
Verify source, destination, TTL and protocol fields.
01
Predict the /26 boundary
Before building, calculate the network containing 192.0.2.10/26 and decide whether 192.0.2.20 is local.
Write it firstNetwork: 192.0.2.0. Broadcast: 192.0.2.63. The kernel should create a connected route for 192.0.2.0/26.
02
Prepare and build
Create two endpoints on one isolated bridge.
Ubuntu
chmod +x mission-act1-labs.sh
sudo ./mission-act1-labs.sh lab02 doctor
sudo ./mission-act1-labs.sh lab02 build03
Ask the kernel
Do not infer the route from the diagram. Read the address and route Linux installed.
Inspect
sudo ./mission-act1-labs.sh lab02 inspect
sudo ./mission-act1-labs.sh lab02 verifyKernel proof
ip route get should select eth0 without a gateway because both endpoints are inside the same /26.04
Read the IPv4 header
Capture a bounded exchange and compare its addresses with the kernel state.
Capture
sudo ./mission-act1-labs.sh lab02 capture
sudo tcpdump -nn -vv -r results/*-lab02/ipv4-header.pcap- Source
- 192.0.2.10
- Destination
- 192.0.2.20
- Protocol
- ICMP inside IPv4
05
Explain identity versus location
The IP address locates an interface in this topology. The Ethernet MAC moves the frame across this one local link.
Exit statementExplain why changing the prefix can change a routing decision even when the numeric IP address stays the same.
06
Close cleanly
Cleanup
sudo ./mission-act1-labs.sh lab02 destroy