Auto-MDIX and speed / duplex auto

March 12th, 2013 | Tags: , , , ,

Auto-MDIX is enabled by default on all 3560 interfaces. In order this feature to work, you should however use speed and duplex auto on the interface. So this is one of the reasons, why you don’t want to hardcode speed and duplex settings ( at least during your CCIE Lab exam)

Auto-MDIX can be disabled with the following command: no mdix auto

You can verify the feature:

sh controllers ethernet-controller gi0/27 phy

GigabitEthernet0/27 (gpn: 27, port-number: 27)
———————————————————–
0000: 1140 Control Register                      :  0001 0001 0100 0000
0001: 796D Control STATUS                        :  0111 1001 0110 1101
0002: 0020 Phy ID 1                              :  0000 0000 0010 0000
0003: 63B0 Phy ID 2                              :  0110 0011 1011 0000
0004: 0181 Auto-Negotiation Advertisement        :  0000 0001 1000 0001
0005: CDE1 Auto-Negotiation Link Partner         :  1100 1101 1110 0001
0006: 000F Auto-Negotiation Expansion            :  0000 0000 0000 1111
0007: 2001 Next Page Transmit                    :  0010 0000 0000 0001
0008: 0000 Next Page Receive                     :  0000 0000 0000 0000
0009: 0400 1000BaseT Control                     :  0000 0100 0000 0000
000A: 0000 1000Base-T Status                     :  0000 0000 0000 0000
000F: 3000 IEEE Extended Status                  :  0011 0000 0000 0000
0010: 4001 Phy Extended Control                  :  0100 0000 0000 0001
0011: 2323 Phy Extended Status                   :  0010 0011 0010 0011
0012: 0000 Receive Error Counter                 :  0000 0000 0000 0000
0013: 00FF False Carrier Sense Counter           :  0000 0000 1111 1111
0014: 1413 Receiver NOT_OK Counter               :  0001 0100 0001 0011
0019: FD1C Auxiliary Status Summary              :  1111 1101 0001 1100
001A: 267E Interrupt Status                      :  0010 0110 0111 1110
001B: FFFF Interrupt Mask                        :  1111 1111 1111 1111
001C: 7CFC Control Reg 2                         :  0111 1100 1111 1100
001D: 0244 Spare Control Register                :  0000 0010 0100 0100
001E: 0080 Test Register 1                       :  0000 0000 1000 0000
 Auto-MDIX                             :  Off   [AdminState=1   Flags=0x000108C8]

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