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OSPF Cheat Sheet
| OSPF – Interior Gateway Protocol (IGP) | |
| Type: | Link State |
| Algorithm: | Dijkstra |
| Metric: | Interface cost is auto-derived from bandwidth unless manually configured. Cost = reference-bandwidth / bandwidth Default reference-bandwidth = 100 000 000 (100 Mbps) |
| External Metrics: | Type 1: The sum of the internal costs plus the external cost. Type 2: Only the external cost assigned by the ASBR. |
| Preference (AD): | 10 / 150 ( Internal / External ) |
| OSPF – Neighborship Requirements | |
| Area | Area ID must match. |
| Area type | Stub flags must match. |
| Authentication | Both authentication type and key must match. |
| Subnet | Subnet must match, both IP address and mask. |
| Timers | Timers must match, both hello and dead interval. |
| MTU | MTU must match. |
| Interface type | Interface type (nbma/p2mp/p2p) must match. |
| Protect-RE | Bonus: Protect-RE firewall filter must allow OSPF packets to RE. |