Two subnets joined by a router

Objective

PC1 (10.0.0.0/24) and PC2 (10.0.1.0/24) talk through router R1; a TCP download crosses it.

Procedure

1. Press Run: ping and the TCP transfer both work.
2. Open Packet capture and check the TTL: 64 at the sender, 63 after one router.
3. Clear PC2's gateway and run again: replies cannot return, the pings fail.

Theory

Hosts send off-subnet packets to their default gateway. The router looks up the destination in its routing table, decrements the TTL and forwards out of the right port.

Network blocks used

2 × Host / PC, Router

More Routing and security experiments

• Firewall rules
• DHCP and DNS server