07-25-2018 07:27 AM - edited 03-08-2019 03:44 PM
Hi all,
I need to understand the speed and duplex settings of the port. I am trying to hard code the speed and duplex settings of the interface which apparently seems a simple procedure. So far what i have learned is you can hard code the interface speed and duplex settings. But in my lab i have the following situation.
Status "notconnect"
SW-3560 <-----------------------------> SW-2960
speed 100 speed 100
duplex full duplex full
Status "notconnect"
SW-3560 <-----------------------------> SW-2960
speed 100 speed 100
duplex auto duplex auto
Status "notconnect"
SW-3560 <-----------------------------> SW-2960
speed auto speed auto
duplex full duplex full
Status "connected"
SW-3560 <-----------------------------> SW-2960
speed 100 speed auto
duplex full duplex auto
****** no "DUPLEX MISMATCH DISCOVERED" log messages ******
Status "connected"
SW-3560 <-----------------------------> SW-2960
speed auto speed 100
duplex auto duplex full
******* "DUPLEX MISMATCH DISCOVERED" log messages on both switches ******
**** if i run "sh controllers ethernet-controller fa 0/4" command on both switches. I can see collisions on 3560 interface in the "TRANSMIT" column and similarly on 2960 in the "RECIEVE" column.
Ports on both these switches are 10/100 capable.
I have tried to go through books, cisco online documents and previous community threads but so far i could not find anything which can explain this behaviour of the interface.
Any idea why is this?
Many thanks.
Solved! Go to Solution.
07-25-2018 09:32 PM - edited 07-25-2018 09:32 PM
@johnlloyd_13 wrote:
OP talks about old 3560 and 2960 switches which uses FE/100M ports.
Nope. I disagree.
Auto-negotiate feature was significantly improved since the introduction of the 3650/3750 and 2960 (compared to 2940/2950/2955 and 3550).
My rule-of-thumb is simple: If the switch supports MDI/MDI-X, then leave the ports to auto-negotiate unless otherwise.
07-26-2018 04:28 AM
07-26-2018 06:03 AM
07-25-2018 07:57 AM
07-25-2018 08:19 AM - edited 07-25-2018 08:21 AM
Thank you for your reply,
I have already gone through this document. Even if I set speed on both sides without making any change to other settings of the interface, even then the link goes down as I mentioned in my post. So something like below,
Status "notconnect"
SW-3560 <-----------------------------> SW-2960
speed 100 speed 100
duplex not set duplex not set
One thing more, that is
on 3560 i am using IOS Version 12.2(44)SE5
on 2960 i am using IOS Version 15.0(2)SE10a
Many thanks,
Kind Regards
Shoaib
07-25-2018 09:01 AM
Hello,
are these 'real' switches, or are you using a simulator ?
07-25-2018 09:12 AM
07-25-2018 03:54 PM
If the gear are Cisco branded, it is no longer "best practice" to hard code speed and duplex on copper ports. This is old, old, old school (mostly taught in Cisco courses and "old timers") & can make matters worst.
07-25-2018 05:36 PM
07-25-2018 06:51 PM
07-25-2018 07:52 PM
hi leo,
OP talks about old 3560 and 2960 switches which uses FE/100M ports. so it's still valid to hardcode and troubleshoot speed/duplex settings on these switches.
gigabitethernet technology fixed this issue and most of the time works when left in auto/auto.
07-25-2018 09:32 PM - edited 07-25-2018 09:32 PM
@johnlloyd_13 wrote:
OP talks about old 3560 and 2960 switches which uses FE/100M ports.
Nope. I disagree.
Auto-negotiate feature was significantly improved since the introduction of the 3650/3750 and 2960 (compared to 2940/2950/2955 and 3550).
My rule-of-thumb is simple: If the switch supports MDI/MDI-X, then leave the ports to auto-negotiate unless otherwise.
07-26-2018 03:54 AM - edited 07-26-2018 03:56 AM
Thank you for your reply Leo.
I am using cat 6 straight cable. I will check with crossover cable and let you know.
Both switches support MDI-X feature. I think you are correct.
One more thing. Please see below,
Status "connected"
SW-3560 <-----------------------------> SW-2960
speed auto speed 100 <--- if manually set
duplex auto ("a-half") duplex full <--- and set full
MDI-X on MDI-X off
Status "connected"
SW-3560 <-----------------------------> SW-2960
speed auto speed auto <--- if set auto
duplex auto ("a-full") duplex full <--- and set full
MDI-X on MDI-X off
So 3560 is not picking up the correct duplex when i change speed on 2960 whereas 2960 does if i do the opposite. Is there any general explanation or this is just an isolated switch problem.
Many thanks.
07-26-2018 04:06 AM
07-26-2018 04:19 AM
This is what I have.
2960
Switch Ports Model SW Version SW Image
------ ----- ----- ---------- ----------
* 1 50 WS-C2960-48TC-L 15.0(2)SE10a C2960-LANBASEK9-M
3560
Switch Ports Model SW Version SW Image
------ ----- ----- ---------- ----------
* 1 52 WS-C3560-48PS 12.2(55)SE9 C3560-IPSERVICESK9-M
Many thanks.
07-26-2018 04:25 AM
@ShoaibM wrote:
Status "connected"
SW-3560 <-----------------------------> SW-2960
speed auto speed 100 <--- if manually set
duplex auto ("a-half") duplex full <--- and set full
MDI-X on MDI-X off
Status "connected"
SW-3560 <-----------------------------> SW-2960
speed auto speed auto <--- if set auto
duplex auto ("a-full") duplex full <--- and set full
MDI-X on MDI-X off
And what is the result if both sides are set to auto speed and auto duplex?
07-26-2018 04:31 AM
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