How routers select paths, NAT changes address representation, and redundant first-hop gateways maintain local network access.
Routing forwards IP packets toward a destination according to routes and next hops. NAT modifies address or port information at a boundary; it does not replace routing.
| Mechanism | Role |
|---|---|
| Static route | Explicit path configured by an administrator |
| Dynamic routing | Routes learned and maintained through a routing protocol |
| Default route | Path used when no more-specific route exists |
| NAT | Translates address representation across a boundary |
| PAT | Lets multiple internal flows share an address by tracking transport ports |
| First-hop redundancy | Keeps a default-gateway function available when a gateway fails |
Route selection normally prefers a matching route with the longest prefix; other selection details depend on the platform and routing source.