=== Computer networking event (22 May 2026) ===

Hi! welcome to our workshop! Today we'd like to show a few things that you can do with computer networks!


==== 1. How does the LAN works (single subnet) ====

  - Set up the static IP addresses
    - Device IP: 192.168.1.x/24 (each participant has number from 1 to 254)
    - Mask: 255.255.255.0
    - Gateway IP: 192.168.1.253
  - Open the wireshark
    - use an "arp || icmp" as in a filter (that will show only ARP and ping messages)
  - Ping the other people IPs
  - Take a look at the ARP table in computer
    - command "arp -a" in windows
    - command "arp -n" in linux (net-tools have to be installed)

| {{:modeemi:pub:workshop22052026-pic1.png?400&units:%|}} |
| Local area network (4 participants) |

    
==== 2. Connect the local area networks into bigger one ====

Each group (2-3 people) has it's own router (with OpenWRT).
One person should set up the router, together with rest of group, from one computer over the web interface (accessible over 192.168.1.1 - and later over 10.1.x.1 address from browser).


Set up following stuff:
  - Set different network IP addresses (IPv4)
    - First router - 10.1.1.0/24
    - Second router - 10.1.2.0/24
    - Third router - 10.1.3.0/24
    - Fourth router - 10.1.4.0/24
  - Reconnect to the router (so that Your computer gets NEW ip from router)
  - Connect WAN port of all routers to common switch
  - Set up WAN interfaces (static IPs)
    - First router - 10.1.5.1/24
    - Second router - 10.1.5.2/24
    - Third router - 10.1.5.3/24
    - Fourth router - 10.1.5.4/24
  - Set up firewalls
    - Forwarding between LAN and WAN has to be always allowed
    - Disable the masquerade

Now time to verify:
  - Ping people in the same subnet (behind the same router)
  - Ping people in the other subnet (behind the other router)
  - Traceroute the people in the other subnet, and take a look what are the routers the packet goes through
  - Take a look with wireshark at all the packets


| {{:modeemi:pub:workshop22052026-pic2.png?600&units:%|}} |
| Interconnected LAN networks |

==== 3. Set up point to point VPN (for next event) ====

  - Install wireguard in openwrt
  - Then set it up with helpful instructions from this page

==== 4. Turn Chromebook into cursed router (for next event) ====

  - we will find commands on the fly
    - ip route add
    - ip addr add
    - and others:D

==== Useful configurations ====

1. VPN project - two sites
  - first with 10.1.1.0/24 network, VPN server
  - second with 10.1.2.0/24 network, VPN client
  - first has 10.1.3.1/30, second has 10.1.3.2/30

Server:
<code>
[Interface]
PrivateKey = yourPrivateKey
Address = 10.1.3.1/30
ListenPort = 51820
PostUp = ip route add 10.1.2.0/24 via 10.1.3.2

[Peer]
PublicKey = OtherpartyPublicKey
AllowedIPs = 10.1.2.0/24, 10.1.3.2/32
</code>

Client:
<code>
[Interface]
Address = 10.1.3.2/30
PrivateKey = yourPrivateKey
PostUp = ip route add 10.1.1.0/24 via 10.1.3.1

[Peer]
PublicKey = OtherPartyPublickey
Endpoint = publicIP:51820
AllowedIPs = 10.1.1.0/24, 10.1.3.1/32
PersistentKeepalive = 21
</code>

==== Useful commands ====

Generate private and public key for VPN server
<code>
wg genkey | tee privatekey | wg pubkey > publickey; cat publickey; cat privatekey
</code>