Forcing speed and duplex is causing interface to go down

[SethRBeavers]

I have a switch 3560v2 Fa0/24 speed 100, duplex full connected to a switch 3560G Gi0/24 speed auto, duplex auto

Encapsulation dot1q

mode trunk

works

As soon as I change the 3560G Gi0/24 to a speed 100 or a duplex full the interface goes down. I can't figure it out and any help would be appreciated. The CLI output is below. I do realize that this is not necessary and when in auto mode both switches go to speed a-100 and duplex a-Full but for peace of mind I would like to hard code these. 

Also, the Gi0/24 interface is built into Vlan2 can some explain to me why the vlan1 goes up and down with the link?

SW1(config-if)#speed 100
SW1(config-if)#
*Mar 1 00:46:40.536: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down
*Mar 1 00:46:41.518: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/24, changed state to down
*Mar 1 00:46:42.533: %LINK-3-UPDOWN: Interface GigabitEthernet0/24, changed state to down

---------------------------------------------------

SW1(config-if)#do sh vlan

VLAN Name          Status      Ports
1       default         active      Gi0/1 - 23 Gi0/25 - 28
2       SW1Trunk    active      Gi0/24

------------------------------------------------------

SW1(config-if)#shutdown
*Mar 1 00:49:05.307: %LINK-5-CHANGED: Interface GigabitEthernet0/24, changed state to administratively down

SW1(config-if)#no shutdown
*Mar 1 00:49:15.239: %LINK-3-UPDOWN: Interface GigabitEthernet0/24, changed state to down

SW1(config-if)#do sh int gi0/24 status

Port Name   Status        Vlan Duplex Speed    Type
Gi0/24     notconnect      2       full     100    10/100/1000BaseTX

SW1(config-if)#do sh int gi0/24
GigabitEthernet0/24 is down, line protocol is down (notconnect)
Hardware is Gigabit Ethernet, address is ******
MTU 9000 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
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
Last input 00:03:30, output 00:03:01, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
91 packets input, 17878 bytes, 0 no buffer
Received 55 broadcasts (31 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 31 multicast, 0 pause input
0 input packets with dribble condition detected
593 packets output, 42410 bytes, 0 underruns
0 output errors, 0 collisions, 3 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

[chrihussey]

Hello,

Changing the speed and duplex settings should cause the port to bounce, but as long as the settings are the same on both sides it should work. However, I can't test this, but the fact that you have both sides hard coded, you may need to then use a cross over cable. That would be the case if both switches were Fast Ethernet interfaces. Auto negotiation with the Gig E interface may be compensating for that fact.

VLAN 1 may be going down because your example shows it configured as a trunk interface, which would allow VLAN 1, and it would be the trunk's native VLAN regardless.

Finally, auto negotiation should work just fine. If they negotiate to 100/full, I wouldn't expect there to be issues.

Hope this helps.

[FBMTRAV]

Try setting the speed and duplex manually on both trunk ports. Make sure you make the change on the remote (edge) switch first. Also see if you have the switchport nonegotiate command available on both ends. 

[FBMTRAV]

As a side note, I have all my trunk links auto negotiate and no issues.

[Leo Laohoo]

Forcing the speed and duplex setting disables MDI/MDI-X. So the question I want to ask is "what kind of cable is used on this port: Straight-through or cross-over?"
NOTE: This is one of the main reason why I leave speed and duplex settings to auto-negotiate.

[Joseph W. Doherty]

I too, with Leo, with wonder whether you have the incorrect cable because as Leo notes, auto MDI/MDI-X is disabled when you disable auto.

BTW, why are you disabling auto as it's been recommended by the network vendors for years now? Working with 20th century devices?