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OSPF Interface Cost Table
The OSPF protocol finds the most efficient route between two points. To find this route, it looks at factors such as interface link speed, the number of hops between points, and other metrics. By default, OSPF uses the actual link speed of a device to calculate the total cost of a route. You can set the interface cost manually to help maximize efficiency if, for example, your gigabyte-based firewall is connected to a 100M router. Use the numbers in this table to manually set the interface cost to a value different than the actual interface cost.
| Interface Type | Bandwidth in bits/second | Bandwidth in bytes/second | OSPF Interface Cost |
|---|---|---|---|
| Ethernet | 1G | 128M | 1 |
| Ethernet | 100M | 12.5M | 10 |
| Ethernet | 10M | 1.25M | 100 |
| Modem | 2M | 256K | 500 |
| Modem | 1M | 128K | 1000 |
| Modem | 500K | 62.5K | 2000 |
| Modem | 250K | 31.25K | 4000 |
| Modem | 125K | 15625 | 8000 |
| Modem | 62500 | 7812 | 16000 |
| Serial | 115200 | 14400 | 10850 |
| Serial | 57600 | 7200 | 21700 |
| Serial | 38400 | 4800 | 32550 |
| Serial | 19200 | 2400 | 61120 |
| Serial | 9600 | 1200 | 65535 |