On a properly functioning router, such as the MikroTik hAP (RB951Ui-2nD), the electrical resistance between the Ethernet lines «Rx» and «Tx» should be 150 ohms ±4%.
Otherwise, the Ethernet port (RJ-45) on the router being tested may have been damaged due to a static overvoltage.
Description of Ethernet Rx and Tx line contacts
Contacts 1 and 2 (white-orange, orange) are used for transmitting (Tx) information (signals), while contacts 3 and 6 (white-green, green) are used for receiving (Rx). The 150 ohm value is made up of two 75 ohm «terminal» resistors. Terminating resistors - are present in almost all network devices that have an Ethernet (RJ-45) port to suppress common-mode interference.