Differences

This shows you the differences between two versions of the page.

--- modeemi:pub:computer-networking-event-22052026 [2026/05/17 17:31] – created niko
+++ modeemi:pub:computer-networking-event-22052026 [2026/05/24 09:50] (current) – [1. How does the LAN works (single subnet)] niko
@@ Line 4: / Line 4: @@
+==== 1. How does the LAN works (single subnet) ====
-==== 1. How does the networks function? ====
+  - 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)
-The following points will be discussed:
+| {{:modeemi:pub:workshop22052026-pic1.png?400&units:%|}} |
-  - IP addresses (IPv4)
+| Local area network (4 participants) |
-    - Gateway
-    - Broadcast
-    - Network
-  - Local network
-    - Set it up
-    - Take a look at packets (wireshark)
-  - Beyond local network - connecting many networks!
+==== 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 ====
+. 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>