VPS Packet Routing & iptables Table (Conceptual)
This table shows how packets are routed through a dedicated server to a VPS instance. It is designed for learning purposes and demonstrates NAT, forwarding, and firewall concepts.
This table shows how packets are routed through a dedicated server to a VPS instance. It is designed for learning purposes and demonstrates NAT, forwarding, and firewall concepts.
Legend / Key
- WAN: Public Internet interface of the dedicated server
- Host: Dedicated server hosting the VPS
- VPS: Virtual machine with private IP assigned by the host
- PREROUTING / POSTROUTING: NAT chains for inbound/outbound traffic
- FORWARD: Packet forwarding chain for routed traffic
- INPUT / OUTPUT: Packets destined to/from the host itself
- DNAT / SNAT: Destination / Source NAT to translate IPs and ports
Packet Flow Table (Conceptual)
| Packet Type / Source | Destination | Chains Traversed | Action / Conceptual Effect |
| Incoming SSH from WAN | VPS private IP | PREROUTING (nat) → FORWARD (filter) | DNAT maps WAN port → VPS port; forwarded to VPS; firewall allows SSH only |
| Incoming HTTP from WAN | VPS private IP | PREROUTING (nat) → FORWARD (filter) | DNAT maps WAN port 80 → VPS port 80; FORWARD allows traffic; connection tracking manages replies |
| Outgoing traffic from VPS to Internet | WAN / Internet | FORWARD (filter) → POSTROUTING (nat) | SNAT translates VPS private IP → Host public IP; ensures return packets come back |
| Host management traffic (SSH to host) | Host IP | INPUT (filter) | Host firewall allows or denies management access |
| VPS internal traffic to Host | Host IP | FORWARD (filter) | Allow/deny access depending on policies (for services like monitoring, backups) |
| VPS-to-VPS (on same host) | VPS internal IP | FORWARD (filter) | Internal routing within host; may bypass NAT |
Notes / Best Practices (Conceptual)
- Use **DNAT** for exposing VPS services to WAN.
- Use **SNAT/MASQUERADE** for outbound VPS traffic.
- Always apply **stateful filtering**: allow ESTABLISHED/RELATED to simplify firewall rules.
- Separate **host management traffic** from VPS traffic with specific chains or interfaces.
- Use **custom chains** for each VPS if hosting multiple instances to simplify rule management.
- Test all rules in a lab environment to avoid locking yourself out of the host or VPS.