This repository contains my solutions and explanations for the NetPractice project from the 42 curriculum.
NetPractice is a networking project focused on configuring IPv4 addresses, subnet masks, gateways, and routing tables to make different hosts communicate correctly.
The purpose of this repository is not just to store the final answers, but to document the way I think through each level, how I split the network, how I choose valid subnets, and how I debug routing errors.
This guide is written as a study reference for myself and for anyone learning the basics of networking through NetPractice.
.
├── README.md
├── img/
│ ├── level1.png
│ ├── level2.png
│ ├── level3.png
│ ├── level4.png
│ ├── level5.png
│ ├── level6.png
│ ├── level7.png
│ ├── level8.png
│ ├── level9.png
│ └── level10.png
└── solution/
├── level1.json
├── level2.json
├── level3.json
├── level4.json
├── level5.json
├── level6.json
├── level7.json
├── level8.json
├── level9.json
└── level10.json
| Folder | Description |
|---|---|
img/ |
Contains screenshots for every solved level |
solution/ |
Contains the exported NetPractice JSON configuration files |
README.md |
Contains the explanation, concepts, and level walkthroughs |
When you open NetPractice, you will see two modes:
Training
Evaluation
Training mode is used for practice.
In this mode, you can solve the levels one by one and move between them freely.
After solving a level, click:
Get my config
to export the configuration as a .json file.
This is the file saved in this repository under:
solution/
Example:
solution/level1.json
Evaluation mode is the real project validation mode.
In the 42 evaluation, you usually need to solve the levels within a limited time.
A good target is:
Less than 15 minutes
To be ready for evaluation, practice until you can:
- Read the topology quickly.
- Identify subnets without guessing.
- Configure gateways correctly.
- Add router routes without creating loops.
- Fix errors by reading the logs.
Before going to evaluation mode, solve the levels in order:
Level 1 -> Level 2 -> Level 3 -> ... -> Level 10
Do not jump directly to the final levels.
The levels build on each other:
- Early levels teach direct communication and subnet masks.
- Middle levels introduce gateways and routers.
- Later levels combine routing tables, reverse paths, Internet routes, and troubleshooting.
My strategy during evaluation is:
- Start with the easiest directly connected networks.
- Configure host IPs and masks first.
- Configure gateways only after the local networks are correct.
- Configure router routes.
- Configure Internet reverse routes.
- Press
Check again. - Read the first real error in the log.
- Fix one problem at a time.
Do not randomly change values.
Most mistakes come from:
Wrong subnet
Wrong gateway
Missing reverse route
Network or broadcast address used as host IP
Routing loop
The logs are very useful because they show the exact path of the packet.
Example:
Forward way: A -> B
on A: packet accepted
on A: send to A1
on B: packet accepted
on B: destination IP reached
This means the forward path worked.
For a complete success, the reverse path must also work:
Reverse way: B -> A
on B: packet accepted
on B: send to B1
on A: packet accepted
on A: destination IP reached
If the forward path works but the reverse path fails, the problem is usually a missing return route.
If the log says:
loop detected
then traffic is probably being sent back to a device it already passed through.
If the log says:
invalid route
then the gateway is probably not directly reachable.
If the log says:
destination does not match any route
then a route is missing.
For this project, we only deal with IPv4.
An IPv4 address is a 32-bit number divided into four blocks. Each block is 8 bits.
Example:
192.168.100.1
In binary:
11000000.10101000.01100100.00000001
Each block can have a value from:
0 to 255
The same binary logic applies to subnet masks.
Example:
255.255.255.0
In binary:
11111111.11111111.11111111.00000000
After a bit becomes 0 in a subnet mask, there cannot be any 1 bits after it.
That is why these values are valid inside masks:
255 = 11111111
254 = 11111110
252 = 11111100
248 = 11111000
240 = 11110000
224 = 11100000
192 = 11000000
128 = 10000000
0 = 00000000
So this is a valid mask:
255.255.255.0
But this is not a valid mask:
255.255.128.128
because after the mask starts using 0 bits, it cannot go back to 1 bits.
An IP address identifies an interface inside a network.
In NetPractice, we do not configure devices directly. We configure their interfaces.
Example:
interface A1
IP: 192.168.1.2
Mask: 255.255.255.0
This means interface A1 belongs to the network:
192.168.1.0/24
Two devices can communicate directly only if they are in the same network, or if there is a router between their networks.
Some IP ranges are reserved for private networks.
These private ranges are:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
The loopback range is:
127.0.0.0 - 127.255.255.255
For NetPractice, the most important thing is not whether an IP is public or private. The most important thing is whether the IP belongs to the correct subnet.
A subnet mask decides which IP addresses are part of the same network.
There are two common ways to write a subnet mask:
Dot-decimal notation: 255.255.255.0
CIDR notation: /24
Example:
192.168.1.10/24
means:
IP: 192.168.1.10
Mask: 255.255.255.0
The first address in a subnet is the network address.
The last address in a subnet is the broadcast address.
Both cannot be assigned to devices.
| CIDR | Dot-decimal Mask | Total IPs | Usable IPs |
|---|---|---|---|
/32 |
255.255.255.255 |
1 | 0 |
/31 |
255.255.255.254 |
2 | 0 |
/30 |
255.255.255.252 |
4 | 2 |
/29 |
255.255.255.248 |
8 | 6 |
/28 |
255.255.255.240 |
16 | 14 |
/27 |
255.255.255.224 |
32 | 30 |
/26 |
255.255.255.192 |
64 | 62 |
/25 |
255.255.255.128 |
128 | 126 |
/24 |
255.255.255.0 |
256 | 254 |
/16 |
255.255.0.0 |
65536 | 65534 |
Example with /30:
Network: 190.3.2.252
Usable: 190.3.2.253
Usable: 190.3.2.254
Broadcast: 190.3.2.255
Only the usable IP addresses can be assigned to interfaces.
A switch connects multiple devices inside the same network.
A switch does not separate networks.
If several devices are connected to the same switch, they usually need to be in the same subnet.
Example:
Host A
Host B
Router interface
If all of them are connected to the same switch, they should share the same network.
A router connects different networks.
A router can have multiple interfaces, and each interface usually belongs to a different subnet.
Example:
R1 interface 1 -> Network A
R1 interface 2 -> Network B
The router can forward packets between these networks only if the routes are correct.
A router does not magically know every network. It only knows:
- Networks directly connected to its own interfaces.
- Networks manually added in its routing table.
A routing table tells a host or router where to send packets.
In NetPractice, a route has two parts:
Destination => Next hop
Example:
192.168.2.0/24 => 192.168.1.1
Meaning:
To reach 192.168.2.0/24, send the packet to 192.168.1.1.
The left side is the destination network.
The right side is the next hop or gateway.
Important rule:
The gateway must be directly reachable.
That means the gateway must be in the same subnet as one of the sender's interfaces.
A default route is used when no more specific route matches.
It can be written as:
default
or:
0.0.0.0/0
Both mean:
Any destination.
Example:
0.0.0.0/0 => 192.168.1.1
This means:
Send all unknown traffic to 192.168.1.1.
To know whether two devices are part of the same network, combine the IP address with the subnet mask.
This is done using a bit-by-bit AND operation.
Example:
IP: 192.168.100.1
Mask: 255.255.255.0
Binary:
IP: 11000000.10101000.01100100.00000001
Mask: 11111111.11111111.11111111.00000000
Result:
11000000.10101000.01100100.00000000
In dot-decimal:
192.168.100.0
So the network is:
192.168.100.0/24
If two devices have the same network address, they are in the same network.
If they are not in the same network, they need a router to communicate.
My solving process:
- Read the goal.
- Identify which hosts need to communicate.
- Split the topology into separate networks.
- Check all directly connected interfaces.
- Make sure devices on the same link are in the same subnet.
- Avoid network and broadcast addresses.
- Set host gateways to the nearest router.
- Add routes on routers for remote networks.
- Add reverse routes when the Internet is involved.
- Read the logs and fix the first real error.
The most important rule:
Do not solve the whole diagram at once.
Split it into small networks first.
| Error | Meaning | Fix |
|---|---|---|
invalid IP address |
The IP is a network or broadcast address | Choose a usable IP |
no route |
A route is missing | Add a route to the destination network |
invalid route |
The gateway is not reachable | Use a gateway in the same subnet |
loop detected |
Traffic is being sent back and forth | Fix wrong default routes |
wrong host |
The IP exists on the wrong device | Check duplicate IPs or overlapping subnets |
no reverse way |
Forward path works but return path is missing | Add the return route |
route match but no interface for gateway |
The gateway is not directly reachable | Use the correct next hop |
Here are the solutions and explanations for all 10 levels.
show
This level has two separate communication goals:
A <--> B
C <--> D
There are no routers and no switches.
Each pair of hosts is directly connected.
The topology can be simplified like this:
A <--> B
C <--> D
So we have two independent small networks:
Network 1: A + B
Network 2: C + D
For the first connection:
A1 = 104.95.23.11
B1 = 104.95.23.12
Mask = 255.255.255.0
This mask is /24.
So both interfaces are inside:
104.95.23.0/24
That means A and B can communicate directly.
For the second connection:
C1 = 211.191.135.75
D1 = 211.191.135.74
Mask = 255.255.0.0
This mask is /16.
So both interfaces are inside:
211.191.0.0/16
That means C and D can also communicate directly.
A gateway is only needed when a device wants to reach another network through a router.
In this level:
A and B are directly connected.
C and D are directly connected.
There is no router.
So no gateway is needed.
Both goals work:
A -> B : OK
C -> D : OK
And the reverse paths also work:
B -> A : OK
D -> C : OK
When two hosts are directly connected, both interfaces must belong to the same subnet.
If they are in the same subnet, they can communicate directly without a gateway.
show
This level has two separate communication goals:
B <--> A
D <--> C
There are still no routers and no switches.
Each pair of hosts is directly connected.
The topology can be simplified like this:
B <--> A
D <--> C
So we have two independent networks:
Network 1: A + B
Network 2: C + D
For the first connection:
A1 = 192.168.99.221
B1 = 192.168.99.222
Mask = 255.255.255.224
The mask 255.255.255.224 is /27.
A /27 subnet increases by blocks of 32 in the last octet:
0, 32, 64, 96, 128, 160, 192, 224
The IP addresses 192.168.99.221 and 192.168.99.222 are inside this subnet:
Network: 192.168.99.192/27
Usable: 192.168.99.193 - 192.168.99.222
Broadcast: 192.168.99.223
So both A1 and B1 are valid usable IP addresses in the same subnet.
That is why A and B can communicate directly.
For the second connection:
C1 = 12.0.0.1
D1 = 12.0.0.2
Mask = 255.255.255.252
The mask 255.255.255.252 is /30.
A /30 subnet has 4 total addresses:
Network address
2 usable host addresses
Broadcast address
For this network:
Network: 12.0.0.0/30
Usable: 12.0.0.1
Usable: 12.0.0.2
Broadcast: 12.0.0.3
So C1 and D1 are exactly the two usable IP addresses.
That is why C and D can communicate directly.
Both goals are between directly connected hosts.
There is no router in this level.
So the devices only need correct IP addresses and masks.
No default gateway is required.
This level is mainly about choosing a valid subnet mask.
The IP address alone is not enough.
You must always check:
IP + Mask
because the mask decides the real network range.
Both goals work:
B -> A : OK
D -> C : OK
And the reverse paths also work:
A -> B : OK
C -> D : OK
Directly connected devices must be in the same subnet.
Also, the IP addresses must not be the network address or the broadcast address.
In this level:
192.168.99.221 and 192.168.99.222 are valid inside 192.168.99.192/27
12.0.0.1 and 12.0.0.2 are valid inside 12.0.0.0/30
show
This level has three communication goals:
A <--> B
A <--> C
B <--> C
All three hosts are connected to the same switch.
The topology can be simplified like this:
Switch S
/ | \
A B C
There is no router in this level.
That means all connected hosts must be part of the same local network.
The switch connects all hosts inside the same network.
A switch does not separate networks. It only forwards traffic between devices connected to it.
So the important rule here is:
A, B, and C must be in the same subnet.
From the successful log, the hosts communicate using these IP addresses:
A = 104.198.223.125
B = 104.198.223.123
C = 104.198.223.124
All of them are inside the same IP range:
104.198.223.x
So they can communicate directly through the switch.
There is no router in this level.
Since all hosts are in the same subnet, packets do not need to leave the local network.
So no default gateway is required.
The hosts can send packets directly to each other through the switch.
Example from Goal 1:
Forward way: A -> B
on A: packet accepted
on A: send to A1
on switch S: pass to all connections
on B: packet accepted
on B: destination IP reached
This means:
- Host A accepted the packet.
- A sent the packet through interface
A1. - The switch forwarded the packet to connected devices.
- Host B received the packet.
- The destination was reached successfully.
In the log, we also see:
on C: packet not for me
This is normal.
Because the switch forwards traffic to connected devices, another host may see the packet but ignore it if the destination IP is not its own IP.
So when A sends a packet to B, host C may receive the packet but rejects it because it is not the destination.
The log also shows:
on A: loop detected
or:
on B: loop detected
In this level, this is not the main problem because the final result is successful.
The important line is:
destination IP reached
The switch tests all connected links, including the sender itself. When the packet is seen again by the original sender, NetPractice marks it as a loop in the log.
As long as the destination is reached and the status is OK, this is not an issue for this level.
All communication goals work:
A -> B : OK
A -> C : OK
B -> C : OK
And the reverse paths also work:
B -> A : OK
C -> A : OK
C -> B : OK
When multiple hosts are connected to the same switch:
They must belong to the same subnet.
A switch does not route traffic between networks.
If the hosts are in different subnets, a router would be needed.
For a switch network, count how many usable IP addresses are needed.
In this level, there are three hosts:
A
B
C
So the subnet must provide at least three usable IP addresses.
A /30 would not be enough because it gives only two usable IP addresses.
A /29 or larger subnet would work because /29 gives six usable IP addresses.
show
This level has three communication goals:
A <--> B
A <--> R
B <--> R
Hosts A and B are connected to the same switch as router R.
The topology can be simplified like this:
Switch S
/ | \
A B R
There is one switch and one router interface connected to that switch.
Even though a router exists in the level, the communication goals are still inside the same local network.
A switch connects devices inside the same network.
In this level, the devices connected to the switch are:
A
B
R
So the interfaces of these devices must belong to the same subnet.
From the successful log, the important IP addresses are:
A = 90.242.111.132
B = 90.242.111.131
R = 90.242.111.130
All of them are in the same IP range:
90.242.111.x
So they can communicate through the switch.
The router R is present, but it is not used to route traffic between different networks in this level.
Here, R behaves like another device connected to the same switch.
That means A, B, and R must all be in the same subnet.
No extra routing table configuration is needed for these goals.
Example from Goal 2:
Forward way: A -> R
on A: packet accepted
on A: send to A1
on switch S: pass to all connections
on R: packet accepted
on R: destination IP reached
This means:
- Host A accepted the packet.
- A sent the packet through interface
A1. - The switch forwarded the packet.
- Router R received the packet.
- The destination was reached successfully.
The log contains lines like:
on R: packet not for me
or:
on A: packet not for me
This happens because the switch forwards traffic to connected links.
If a device receives a packet that is not addressed to its own IP, it ignores it.
This is normal in this level.
The log also contains:
loop detected
In this level, the final result is still correct because the destination is reached.
The switch tests multiple links, including the link back toward the sender.
As long as NetPractice shows OK and the destination is reached, this message is not the main issue here.
All goals work:
A -> B : OK
A -> R : OK
B -> R : OK
The reverse paths also work:
B -> A : OK
R -> A : OK
R -> B : OK
A router interface connected to a switch must be in the same subnet as the other devices on that switch.
The router only becomes useful for routing when traffic needs to leave this local network.
When a switch connects multiple devices, count how many usable IP addresses are needed.
In this level, the switch connects three interfaces:
A1
B1
R1
So the subnet must provide at least three usable IP addresses.
A /30 is not enough because it provides only two usable IP addresses.
A /29 or larger subnet would be enough.
show
This level has three communication goals:
A <--> R
B <--> R
A <--> B
There is one router between two different host networks.
The topology can be simplified like this:
A <--> R <--> B
Router R has two interfaces:
R1 connected to A
R2 connected to B
This means there are two separate networks:
Network 1: A + R1
Network 2: B + R2
Host A and router interface R1 are directly connected.
From the log:
A = 57.202.124.125
R1 = 57.202.124.126
So A and R1 must be in the same subnet.
Host B and router interface R2 are also directly connected.
From the log:
B = 135.233.22.253
R2 = 135.233.22.254
So B and R2 must be in the same subnet.
For Goal 1:
A -> R
A can reach R directly through R1.
For Goal 2:
B -> R
B can reach R directly through R2.
But for Goal 3:
A -> B
A and B are not in the same network.
So A must send the packet to its gateway, which is router R.
The same applies in the reverse direction:
B -> A
B must send the packet to router R.
From Goal 3:
Forward way: A -> B
on A: destination does not match any interface
on A: route match 0.0.0.0/0
on A: send to gateway 57.202.124.126 through interface A1
on R: packet accepted
on R: send to R2
on B: destination IP reached
This shows the correct path:
A -> R -> B
A does not know B directly, so it sends the packet to its gateway:
57.202.124.126
That gateway is router interface R1.
Then the router forwards the packet through R2 to B.
The reverse path is also correct:
B -> R -> A
From the log:
on B: route match default
on B: send to gateway 135.233.22.254 through interface B1
on R: packet accepted
on R: send to R1
on A: destination IP reached
B sends traffic to its gateway:
135.233.22.254
That gateway is router interface R2.
The router then forwards the packet back through R1 to A.
All goals work:
A -> R : OK
B -> R : OK
A -> B : OK
And the reverse paths also work:
R -> A : OK
R -> B : OK
B -> A : OK
When two hosts are in different networks, they need a router between them.
Each host should use the router interface connected to its own network as its gateway.
For two-device links, use the smallest subnet that fits two usable IP addresses.
A /30 is usually enough for:
A <--> R
B <--> R
because /30 gives exactly two usable IP addresses.
show
This level has one main goal:
A <--> Internet
Host A must reach the Internet, and the Internet must be able to send traffic back to A.
The topology can be simplified like this:
A --- Switch S --- R --- Internet
The network is split into two main parts:
A + R
R + Internet
A is not directly connected to the Internet.
So A sends Internet traffic to router R.
Then R forwards the packet to the Internet.
The forward path is:
A -> R -> Internet
The reverse path must also work:
Internet -> R -> A
Host A sends traffic to its gateway:
28.219.87.228
Router R sends Internet traffic to:
163.172.250.1
The Internet sends replies back through:
163.172.250.12
Forward path:
A -> R -> Internet
Reverse path:
Internet -> R -> A
Internet communication needs two directions.
The host needs a default route to the router.
The Internet also needs a reverse route back to the internal network.
Forward routing alone is not enough.
For Internet levels, check this order:
1. Host gateway
2. Router route to Internet
3. Internet reverse route
4. Gateway reachability
Most failures happen because the reverse route is missing or points to the wrong gateway.
show
This level has one main goal:
A <--> C
Host A must communicate with host C through two routers.
The topology can be simplified like this:
A <--> R1 <--> R2 <--> C
The network is split into three parts:
A + R1
R1 + R2
R2 + C
A and C are not directly connected.
So the packet must pass through both routers:
A -> R1 -> R2 -> C
The return path must also work:
C -> R2 -> R1 -> A
This level is mainly about making sure each device sends traffic to the correct next hop.
Host A sends traffic to R1:
107.198.14.1
R1 sends traffic to R2:
107.198.14.253
Host C sends traffic back to R2:
107.198.14.5
R2 sends traffic back to R1:
107.198.14.254
Forward path:
A -> R1 -> R2 -> C
Reverse path:
C -> R2 -> R1 -> A
When traffic crosses multiple routers, every router must know the next hop toward the destination.
The forward path and the reverse path must both be valid.
For this type of topology, solve in this order:
1. Configure the A-to-R1 network.
2. Configure the R1-to-R2 network.
3. Configure the R2-to-C network.
4. Add the forward route from A toward C.
5. Add the reverse route from C back toward A.
Do not guess routes randomly.
Split the topology into small networks first.
show
This level has three goals:
C <--> D
C <--> Internet
D <--> Internet
Hosts C and D must communicate with each other, and both hosts must also reach the Internet.
The topology can be simplified like this:
C ----\
R2 ---- R1 ---- Internet
D ----/
The network is split into four main parts:
C + R2
D + R2
R2 + R1
R1 + Internet
C and D are not directly connected to the Internet.
They both use R2 as their gateway.
Then R2 forwards traffic to R1.
Finally, R1 forwards traffic to the Internet.
The main path is:
C/D -> R2 -> R1 -> Internet
For the return traffic, the Internet must know how to reach the internal network.
So the reverse path is:
Internet -> R1 -> R2 -> C/D
Host C sends traffic to:
128.24.243.1
Host D sends traffic to:
128.24.243.25
Router R2 sends Internet traffic to R1:
128.24.243.62
Router R1 sends Internet traffic to:
163.225.250.1
The Internet sends replies back through:
163.225.250.12
Internal communication:
C -> R2 -> D
D -> R2 -> C
Internet communication:
C -> R2 -> R1 -> Internet
D -> R2 -> R1 -> Internet
Reverse Internet communication:
Internet -> R1 -> R2 -> C
Internet -> R1 -> R2 -> D
This level is about complete routing.
Forward routing alone is not enough.
The reverse path must also work, especially when the Internet is involved.
show
This level has six goals:
A <--> B
C <--> D
A <--> Internet
A <--> D
B <--> C
C <--> Internet
It combines switch communication, multiple routers, host gateways, Internet routing, and reverse paths.
The topology can be simplified like this:
A ----\
Switch S ---- R1 ---- Internet
B ----/ |
|
R2
/ \
C D
The network is split into five main parts:
A + B + R1
R1 + Internet
R1 + R2
C + R2
D + R2
A and B are in the same switch network, so they can communicate directly.
C and D are behind R2, so they use R2 as their gateway.
For traffic between the upper network and the lower networks, packets must pass through:
R1 -> R2
For Internet traffic, packets go through:
Internal host -> Router -> Internet
and the Internet must also have a valid route back to the internal networks.
Hosts A and B use R1 as their gateway:
12.168.63.1
Host C uses R2 as its gateway:
1.0.0.2
Host D uses R2 as its gateway:
18.124.23.219
R1 sends traffic to the networks behind R2 through:
163.172.250.253
R2 sends traffic back toward R1 through:
163.172.250.254
The Internet sends replies back through:
163.172.250.12
Local switch communication:
A -> Switch -> B
B -> Switch -> A
Internal communication behind R2:
C -> R2 -> D
D -> R2 -> C
Communication between upper and lower networks:
A/B -> R1 -> R2 -> C/D
C/D -> R2 -> R1 -> A/B
Internet communication:
A -> R1 -> Internet
C -> R2 -> R1 -> Internet
Reverse Internet communication:
Internet -> R1 -> A
Internet -> R1 -> R2 -> C
This level is about connecting multiple smaller networks together.
The switch keeps A, B, and R1 in the same local network.
The routers connect the different networks.
The Internet route must also support the reverse path, not only the forward path.
Solve this level in this order:
1. Make A and B communicate through the switch.
2. Make C and D communicate through R2.
3. Connect R1 and R2.
4. Add routes between the upper and lower networks.
5. Add Internet routes.
6. Verify the reverse paths.
Do not start with the Internet.
Start with local networks first, then connect them together.
show
This is the final NetPractice level.
It has seven goals:
H1 <--> H2
H3 <--> H4
H1 <--> Internet
H1 <--> H4
H2 <--> H3
H3 <--> Internet
H4 <--> Internet
This level combines switch networks, multiple routers, host gateways, Internet routing, and reverse paths.
The topology can be simplified like this:
H1 ----\
Switch S1 ---- R1 ---- Internet
H2 ----/ |
|
R2
/ \
H3 H4
The network is split into five main parts:
H1 + H2 + R1
R1 + Internet
R1 + R2
H3 + R2
H4 + R2
H1 and H2 are in the same switch network, so they can communicate directly.
H3 and H4 are behind R2, so they use R2 as their gateway.
Traffic between the upper switch network and the lower hosts must pass through:
R1 -> R2
Internet traffic from the lower hosts must pass through:
H3/H4 -> R2 -> R1 -> Internet
For the return traffic, the Internet sends packets back to R1, then R1 forwards them either to the switch network or to R2.
H1 and H2 use R1 as their gateway:
162.74.222.1
H3 uses R2 as its gateway:
162.74.222.250
H4 uses R2 as its gateway:
162.74.222.129
R1 sends traffic to the networks behind R2 through:
162.74.222.253
R2 sends traffic back toward R1 through:
162.74.222.254
The Internet sends replies back through:
163.172.250.12
Local switch communication:
H1 -> Switch S1 -> H2
H2 -> Switch S1 -> H1
Internal communication behind R2:
H3 -> R2 -> H4
H4 -> R2 -> H3
Communication between upper and lower networks:
H1/H2 -> R1 -> R2 -> H3/H4
H3/H4 -> R2 -> R1 -> H1/H2
Internet communication:
H1 -> R1 -> Internet
H3/H4 -> R2 -> R1 -> Internet
Reverse Internet communication:
Internet -> R1 -> H1/H2
Internet -> R1 -> R2 -> H3/H4
Level 10 does not introduce one new idea.
It combines all previous ideas:
Switch = same local network
Router = separates networks
Gateway = next hop
Routing table = path to remote networks
Internet route = needs reverse path
The correct method is to solve local networks first, router links second, and Internet routes last.
For the final level, use this order:
1. Check H1 and H2 on the switch network.
2. Check H3 and H4 behind R2.
3. Check the R1-to-R2 link.
4. Add routes between upper and lower networks.
5. Add Internet routes.
6. Verify reverse paths.
Do not randomly change routes.
A single wrong default route can create a loop and break multiple goals.
This repository is for learning, review, and documentation.
If you are a 42 student working on NetPractice, try to solve each level by yourself first.
Do not copy the configurations blindly.
The real goal of NetPractice is to understand how IP addressing, subnetting, gateways, and routing tables work.
Completed.
Mohammad Alhindi
- GitHub: @mohammadalhindi1