The RB5009, configured as switch, indicates that link partner is advertising speeds 10Mbps and 100Mbps. There are 3 possibilities (I'm listing them in order of probability, but you may want to check them starting from the simplest check towards the complex ones):
- The cable connectors are iffy ... if connectors are at one edge of tolerances and device connector is on the other, then connection can be iffy. 1Gbps requires use of all 4 wire pairs while for 100Mbps (and 10Mbps) only two pairs are used. If one wire of "additional" pairs is not OK, autonegotiation for 1Gbps will fail and link partners will see as if the other end doesn't advertise 1Gbps.
- cable is terminated non-properly. Either on patch panel or in connectors. Cable has to be terminated in the same way on both ends. There is a standard of doing it with two variants (TIA/EIA 568 A and B) and it's critical to follow the same variant on both ends of cable.
Additionally, if the cable is shielded (STP) - which is a good thing if cable is longer - then the shield should only be grounded (connected to STP connector shield or to patch panel ground) on one side. If the shield is grounded on both ends, stray currents may flow and those can cause more interference in data wires than unshielded (UTP) cable may pass.
- The cable itself is either too long or not properly wired. Maximum distance for ethernet is 100 metres (sometimes it works over slightly longer distances but that's not guaranteed). If wire pairs are untwisted over distance longer than a centimetre or two (in patch panels or wall outlets), then the quality degrades considerably ... possibly to the level when high frequency signals, needed for 1Gbps, don't pass through such wires.
- link partner is set to only advertise 100Mbps and 10Mbps.
- and then there's always possibility of device being broken. As it's PoE-capable, the possibility is higher than with non-PoE variant due to additional elements, needed for PoE to work on each RJ45 port.