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The bridge interface setting port-cost-mode changes the port path-cost and internal-path-cost mode for bridged ports, utilizing automatic values based on interface speed. This setting does not impact bridged ports with manually configured path-cost or internal-path-cost properties. Below are examples illustrating the path-costs corresponding to specific data rates (with proportionate calculations for intermediate rates):
| Data rate | Long | Short |
|---|---|---|
| 10 Mbps | 2,000,000 | 100 |
| 100 Mbps | 200,000 | 19 |
| 1 Gbps | 20,000 | 4 |
| 10 Gbps | 2,000 | 2 |
| 25 Gbps | 800 | 1 |
| 40 Gbps | 500 | 1 |
| 100 Gbps | 200 | 1 |
For bonded interfaces, the highest path-cost among all bonded member ports is applied, this value remains unaffected by the total link speed of the bonding. For virtual interfaces (such as VLAN, EoIP, VXLAN), as well as wifi, wireless, and 60GHz interfaces, a path-cost of 20,000 is assigned for long mode, and 10 for short mode. For dynamically bridged interfaces (e.g. wifi, wireless, PPP, VPLS), the path-cost defaults to 20,000 for long mode and 10 for short mode. However, this can be manually overridden by the service that dynamically adds interfaces to bridge, for instance, by using the CAPsMAN datapath.bridge-cost setting. RouterOS versions prior to 7.13 does not change port path cost based on the link speed, for 10M, 100M, 1000M, and 10000M link speeds the default path cost value when a port is added to a bridge was always 10.
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