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-metric-value-cost-and-ospf-default-cost-reference-bandwidth.php [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
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