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Pre-standard Cisco PoE also uses FLP for power detection. This FLP power detection method might be "confused" as speed/duplex autonegotiation.
I was able to test this with 2 3750-E switches. In this scenario I am using port 1/0/48 on both switches. The switches are called switch A and switch B
When I set the duplex to full and speed to 100 on switch B switch A's interface shows 100 Full
Here is the config and show command for switch B
Switch-C#sh run in gi1/0/48 Building configuration...
Current configuration : 63 bytes ! interface GigabitEthernet1/0/48 speed 100 duplex full end
Switch-B#sh int gi1/0/48
Keepalive set (10 sec) Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX input flow-control is off, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:08, output 00:00:00, output hang never
Switch A config and show command
Switch-A#sh run int gi1/0/48 Building configuration...
Current configuration : 63 bytes ! interface GigabitEthernet1/0/48 spanning-tree portfast end
Switch-A#sh interfaces gi1/0/48
Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX input flow-control is off, output flow-control is unsupported ARP type: ARPA, ARP Timeout 04:00:00
When auto-negotiation is disabled on one switchport the switch at the other end of the link can use the Parallel detection function to determine the speed. Put simply the switch does not negotiate the speed with the other switch but it can still work it out.
However what it cannot work out without auto-negotiation is the duplex. Now as far as i know 10/100 ethernet interfaces default to half-duplex and gigabit interfaces default to full duplex. So you could interprete this to mean the port would set itself to 100 Full because of it's default setting is gigabit.
No sure about 3750v2 but Catalyst 3560v2 behave differently: if you configure both speed and duplex statically on a port, the autonegotiation will not be deactivated but will advertise only a single capability including the preconfigured speed and duplex .This is actually more intuitive and natural behavior but obviously, this is not supported on older switches. Probably it depends on the PHY controllers used in Catalyst switches and they seem to be different between various Catalyst platforms.
This all makes the autonegotiation and all exceptions around it a most cumbersome topic - so my recommendation usually is that either both ends of a link are set to autonegotiation with no static settings, or both speed and duplex are set statically on both link ends. The behavior of autonegotiation on Catalyst switches is not well documented and is obviously platform and version dependent, making it quite hard to remember.
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