Robert, Robert Sander wrote:
On 17.02.20 09:03, Kees Meijs wrote:
The path I'm trying to avoid has the lowest OSPF cost but in the physical world the most... :-) I always thought the OSPF cost represents the "physical" cost of a link.
Not necessarily. From RFC 2328, p. 18 [0]:
A cost is associated with the output side of each router interface. This cost is configurable by the system administrator. The lower the cost, the more likely the interface is to be used to forward data traffic. Costs are also associated with the externally derived routing data (e.g., the BGP-learned routes).
From RFC 2328, p. 66 [0]:
Interface output cost(s) The cost of sending a data packet on the interface, expressed in the link state metric. This is advertised as the link cost for this interface in the router-LSA. The cost of an interface must be greater than zero.
In essence. The interface metric used by OSPF is just an arbitrarily decided value. With every Network Operating System having some built-in values used [3]. But as well, often available to be re-configured by the Systems/Network Administrator if the Network design of choice requires so. Footnotes: ------------------------------------------------------------ [0]: https://www.rfc-archive.org/getrfc?rfc=2328 [1]: https://packetlife.net/media/library/10/OSPF.pdf [2]: https://packetlife.net/media/library/40/IOS_Interior_Routing_Protocols.pdf [3]: https://www.omnisecu.com/cisco-certified-network-associate-ccna/what-is-ospf... [4]: http://docs.frrouting.org/en/latest/ospfd.html#configuring-ospf [5]: http://docs.frrouting.org/en/latest/ospf6d.html#ospf6-router [6]: https://unix.stackexchange.com/questions/381905/ospf-route-costs-in-bird [7]: https://gitlab.labs.nic.cz/labs/bird/wikis/OSPF_example -- Best regards, Chriztoffer