Re: 3650 Speed and Duplex Negotiation fails

nfdschmidt · ‎09-01-2017

Hello Community,

I have a problem with a new 3650 switch from my customer.

They have some branch office with new 3650 switches (IPBase, IOS XE 3.6.4E and 3.6.7E). I update the switches from 3.6.4. to 3.6.7 because of the SNMP-Bug.

The customer renewed his printers (now Kyocera) and the printers does not connect to the switch. Both sides are configured with automatic negotiation. So Speed and Duplex should negotiate the best but nothing happens. The port remains down. MDIX is turned on.

One Note, I know, that it can't be more then 100mbit/full because of the cabling. They use a shared cabling where one cable is used for two network ports in the offices. So only 4 wires (1,2,3,6) can be used.

It seems that the 3650 doesn't fallback to 100mbit because when I just configure the speed to 100 mbit and leave the duplex auto then the printer can connect.

The strange thing is that the same printer (model and software) can connect to an old 3750X with the same shared cabling and the auto negotiation decides 100/full. Here everything works fine.

The support from Kyocera says that they don't know the problem.

Can someone explain this to me or have the same problem?

Best regards,

Daniel

bersoare · ‎09-01-2017

I suspect that the cabling strategy you mentioned might not be working that well. I have never seen a practical use of 2 ports and one cabling.

One thing you can do is to run TDR testing and start from there.

Leo Laohoo · ‎09-01-2017

TDR won't work (well) with a breakout box.

chrihussey · ‎09-01-2017

Different switches, even interfaces have different tolerances. You may be on the cusp where it would work with one and not another. You could try leaving it at auto negotiation and limit it to 10/100 only. In interface mode "speed auto 10 100".
By the way, I have had to do the same thing at times when there were cabling restrictions and more drops were needed.

Leo Laohoo · ‎09-01-2017

CSCvc05366

NOTE: Please be aware that this bug doesn't have any information about which version is "really" affected and what version(s) is/are fixed in.

brannonsweet@cox.net · ‎04-17-2019

We have a similar issue. The switch and a printer are both set to auto negotiate. The port shows down/down. It doesn't negotiate. I have to hard code the switchport to "speed 100" to get the printer to come up.

The network cable is only using 4 wires, pins 1,2,3,6. so I know only 100Mbps is supported here. But shouldn't the switch set the connection to 10/half since it can't negotiate Gig? It's not, and I think their in lies the problem.

Switch:Cisco WS-C3650-24PD

Printer- Hp Laserjet Pro M402n

bersoare · ‎04-17-2019

Hello Brennon,

Have you tried running a TDR test in that port? If autoneg is failing, I'd guess there's something funny with the cable itself.

The TDR would tell you if all 4 pairs are sending/receiving signals and hints you if the link is "open" (bad) and also the cable length (approx)

Leo Laohoo · ‎04-18-2019

brannonsweet@cox.net wrote:

But shouldn't the switch set the connection to 10/half since it can't negotiate Gig? I

Depends on how old the IOS of the switch. I see this very regularly with a very, very old IOS.

Old IOS have "issues" with auto-negotiation.