NET-03 · Educational simulation

IP Routing & Packet Forwarding

One packet, three networks, three routers. Watch each router read the destination, search its routing table, decrement TTL and choose the interface the packet leaves by.

SourcePC-A

Local network192.168.1.0/24

Next hop10.0.0.2

Destination network192.168.2.0/24

ServerServer-B

Destination

React Flow

ReadyStep 0 / 16

The packet is ready at PC-A. Pick a destination and press “Send packet”.

Speed

Explanation

Before you start

PC-A on 192.168.1.0/24 wants to reach a server on another network. Press “Send packet” to watch each router decide where it goes, or “Step” to advance one decision at a time.

Why did the host send the packet to the default gateway?
Keep going — the answer unlocks when the run reaches it.
Why did the router inspect the destination IP?
Keep going — the answer unlocks when the run reaches it.
Which routing-table entry matched?
Keep going — the answer unlocks when the run reaches it.
Why was this interface selected?
Keep going — the answer unlocks when the run reaches it.
What is the next hop?
Keep going — the answer unlocks when the run reaches it.
Why did TTL decrease?
Keep going — the answer unlocks when the run reaches it.

Router inspector

Router-1 (R1)

Router ID: 1.1.1.1
Selected route: —
Next hop: —
Forwarding decision: Has not seen the packet yet

Interfaces

G0/0192.168.1.1/24Network Aup
G0/110.0.0.1/30R1–R2 linkup
G0/210.0.1.1/30R1–R3 linkup

Routing table

CodeDestination networkPrefixNext hopOutgoing interfaceMetricStatus

C192.168.1.0/24connectedG0/00up✓✕

C10.0.0.0/30connectedG0/10up✓✕

C10.0.1.0/30connectedG0/20up✓✕

S192.168.2.0/2410.0.0.2G0/11active✓✕

S172.16.3.0/2410.0.1.2G0/21active✓✕

C = directly connected · S = static · S* = default route. When several entries match, the longest prefix wins.

Packet inspector

No packet yet

Source IP: —
Destination IP: —
Protocol: —
Packet size: —
TTL: —
Current router: —
Incoming interface: —
Outgoing interface: —
Next hop: —
Current state: Ready

Event timeline

0 / 16

Data created--:--:--
Packet created--:--:--
Destination analyzed--:--:--
Default gateway selected--:--:--
Sent to the gateway--:--:--
Router-1 received packet--:--:--
Routing table lookup--:--:--
Route selected--:--:--
TTL decremented: 64 → 63--:--:--
Packet forwarded--:--:--
Router-2 received packet--:--:--
Routing table lookup--:--:--
Destination network selected--:--:--
TTL decremented: 63 → 62--:--:--
Packet forwarded--:--:--
Packet delivered to Server-B--:--:--