┌───────┐                    ║          ┌─────┐           ║                  ┌──────┐            
            Network                   │TelBru │                    ║          │Modem│           ║                  │ WiFi │            
          Connections                 │  WAN  │◀───────────────────╬─────────▶│     │◀──────────╬─────────────────▶│Router│            
                                      └───────┘                    ║          └─────┘           ║                  └──────┘            
                                                                   ║                            ║                                      
     ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ╬ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─║─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─     
                                                                   ║                            ║                                      
                                                                   ║                            ║                                      
                                                                   ║    Outgoing connections    ║                                      
                                                                   ║       work correctly       ║                                      
                                        ◀━━━━━━━━━━━━━━━━━━━━━━━━━━╬━━ through both firewalls ━━╬━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓       
                                                                   ║      (double NAT'ing)      ║                              ┃       
                                                                   ║                            ║                              ▼       
                                                                   ║                            ║                          ╔═══════╗   
                                                                   ║                            ║                          ║  LAN  ║   
                                                                   ║                            ║                          ║Clients║   
                                                                   ║                            ║                          ╚═══════╝   
                                                                   ║     Incoming protocols     ║                              ▲       
                                                                   ║        require port        ║                              ┃       
                                       VPN  ◀━━━━━━━━━━━━━━━━━━━━━━╬━━━━  forwarding setup  ━━━━╬━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┫       
    Firewall Configuration                                         ║     on both firewalls      ║                              ┃       
      and traffic routing                                          ║                            ║                              ┃       
                                                                   ║                            ║                              ┃       
                       ┌───────────────────────────┐               ║                            ║                              ┃       
                       │ Internet entities making  │               ║   Incoming connections     ║    UPnP requests      ┌─────────────┐
                       │inbound connections ,i.e.,:│               ║    can't be setup with     ║    only puncture      │Plex, Online │
                       │  Plex client, VOIP peer,  │◀━┳────────────╬──┼UPnP (port forwarding─ ─ ╬ ─    the first     ─ ─│Gaming, VOIP │
                       │        gaming peer        │  ┃            ║     must be manually       ║    firewall and       └─────────────┘
                       └───────────────────────────┘  ┃            ║        configured)         ║    will not work             ▲       
                                                      ┃            ║                            ║                              ┃       
                                                      ┃            ║    Incoming connections    ║                              ┃       
                                                      ▼            ║    can be automatically    ║                              ┃       
                                             ┌─────────────────┐   ║       established by       ║                              ┃       
                                             │  Intermediary   │   ║    software designed to    ║                              ┃       
                                             │ Internet relay; │   ║   work around firewalls    ║                              ┃       
                                             │   more delay,   │◀──╬───  blocking incoming   ━━━╬━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛       
                                             │ less throughput │   ║    connections by first    ║                                      
                                             └─────────────────┘   ║   setting up an outgoing   ║                                      
                                                                          connection to an                                             
                                                                        intermediary entity                                            
                                                                                                                                       
                                                                                                                                       
                                                                                                                                       
                            Workable for technically the proficient. Outgoing connections will just "work".                            
                            Incoming connections can only be established via intermediaries; even when such                            
                            services are available delay will higher and throughput lower.