When connecting an enterprise network to an ISP, ensuring redundancy is crucial. It can be achieved in several ways, including redundant links and equipment. Redundant links protect against link failures, while redundant equipment ensures connectivity even if one router fails.
For instance, having two redundant internet providers is advisable for critical server hosting. If one ISP network experiences issues, traffic is automatically rerouted through the second ISP. There are four basic ISP connectivity types:
- Single-homed: In this configuration, a network relies on just one service provider, which can pose risks if that provider experiences issues, as there's no backup.
- Dual-homed: Dual-homed networks maintain redundancy using two links from a single ISP. This ensures connectivity even if one link or ISP experiences problems.
- Multihomed: Multihomed networks connect to multiple ISPs, enhancing redundancy and allowing traffic load balancing between these providers.
- Dual-multihomed: This configuration takes redundancy to the next level by employing two links to each ISP, offering the highest level of reliability. However, it can be more costly to implement.