Re: Problem connecting devices in 10 GB

miguel00111 · ‎01-09-2021

Hi,

I installed a Cisco SG350XG-24T in a customer's network. Some 10 GB capable devices work fine (Synology, Mac mini and an iMac Pro). But when I connect a brand new iMac (10 GB capable) to the network from one of the offices it won't get a connection in 10 GB. The cable from the Mac to the wall is a Cat. 7, then there's about 20 meters of Cat. 6 cable to the rack and finally a Cat. 7 cable from the rack to the switch. It doesn't work in 10 GB. If I connect this machine in place of the iMac Pro (Cat. 6 cable from the Mac to the wall + 10 meters of Cat. 6 cable to the rack + Cat. 6a from the rack to the switch it works fine.

My question is, do the different cables need to be the exact same category ?

Any help would be appreciated.

Miguel

TJ-20933766 · ‎01-10-2021

1) Do you have a way to certify the cable or did the installers certify it for you? The usual process is to have a device such as a Fluke (https://www.datacomtools.com/store/flukenetworks-DSX-5000.html) run a series of frequencies over the cable. If the cable installers didn't ensure their twists were tight enough all the way up to the point of punch down on the patch panel or wall jack, then the Fluke will fail the certification. This is the most common problem I see when a device won't negotiate the highest data rate of the interface.

2) Can you take the iMac that will negotiate to 10Gbps to the office of the iMac that won't negotiate at 10Gbps and plug it in? Use the same patch cables and everything and see if the good iMac will negotiate or not. If not then I'd look closer at the cabling. If it will then I'd look closer at that (possibly bad) iMac.

Let me know how it goes and please consider rating helpful posts.

miguel00111 · ‎01-11-2021

Hi Tyson,

Thanks for your tips.

I did some testing and realized that if I connected a "good" machine (working well in 10GB) to another port on the switch it would stop working. The Mac would show that the connection was in 10GB but it wouldn't get a DHCP address.

So I went to the switch configuration and saw that the auto-negotiation for several ports (about 6 of them) wasn't working! I forced it to connect in 10GB and now it works fine. I checked the firmware and it is up to date, so this must be a bug somewhere that Cisco should fix.

Best,

Miguel