SFP support for Cisco C3850 24s-s model

[rajthemisterious]

Hi All,

I recently purchased a Cisco 3850 24 S - S model  (basically , all 24 ports are SFP based and the 4 uplink modules are SFP based as well.)

My question is, if i have to connect another switch whose uplink port is of only 100 Mbps to the downlink (24 ports) ports of the Cisco 3850, which SFP should i buy ? Should it be a Gig SFP ? If I buy the Gig SFP, do i need to change the speed of the interface to 100 Mbps ? is it even possible to change the speed of the fiber port to 100 Mbps if the SFP is of 1Gig ?

Really need your advice here !

[Francesco Molino]

Hi

The sfp copper (glc-t) can operate at 100mbps.
However, the 3850 sfp switch operate at 1G only.
It depends on the hardware and this one cannot operate at 100mbps. I don't have any right now in which i can test.
What is the remote switch model you want to connect? 

[rajthemisterious]

Hello Francesco, thanks for Your reply.

Basically, i have upto 30 of unmanaged Korenix 3705F switches which i want to connect to the Cisco 3850 24S-S switches.

(The Cisco 3850S switch will act as my default gateway for the devices connected to the Korenix switches)

The main thing here is, that the Korenix switches have uplink FIBER ports which are maximum 100 Mbps.

Here is the link of the Korenix switch model for Your perusal.

https://www.korenix.com/en/product/show.aspx?num=21 

Now, these switches are at a distance of more than 100 metres (maximum distance is 400 metres) from my Server room hence i need to use Fiber.

So i need to use fiber ports on cisco.

Also, one more thing.

I stumbled upon this SFP compatibility matrix link (https://tmgmatrix.cisco.com/?dr=1&dr=21&npid=388) from Cisco where in for the Cisco 3850-24S-S model, it says that the 'GLC-GE-100FX'  is compatible.

Going by the name of the SFP, i think it CAN operate at 100Mbps. But I want to be **bleep** sure before i buy them. How can i verify it ? (Again, i want these SFPs to be plugged in the DOWNLINK ports of the 3850 , NOT the uplink ports).

[Leo Laohoo]

GLC-GE-100FX will work.  Take note the maximum distance this wavelength supports.  

Make sure the 3850 is running the minimum correct firmware.  If unsure, just load the latest 16.6.X or 16.9.X or 16.12.X firmware.  

Personally, I would recommend the 9300-24S over the 3850 because the 3850 has some "hardware limitation" which the 9300 won't.  Another reason is the 9300 have another >4 years of "shelf life" while the 3850-12S/24S has <6 months left before the end-of-sale announcement.  

[rajthemisterious]

Hello Leo, 

Thanks to confirm.

Regarding the GLC-GE-100FX SFP, just to recheck again, can i be sure that the DOWNLINK ports of the 3850 will accept this SFP ? I am not concerned of the uplinks, but downlink ports, here.

Also, I have loaded the 3850 with this * marked IOS as per this URL : https://software.cisco.com/download/home/286257125/type/282046477/release/Fuji-16.9.5

Regarding the 9300 versus 3850, i wanted to go with 9300 as well but 'had' to go with 3850 due to cost considerations.

[Leo Laohoo]

Uplink/Downlink ... they are both the same meaning.  It depends when it is going to a client (downlink) or coming from a client (uplink).  

Are you able to compare the price of the 3850-24S vs 9300-24S.  I thought they were meant to be priced the same.  

[rajthemisterious]

Hi,

The 3850 24S-S model has 24 SFP ports which I called as Downlinks and another 4 ports which are card based which I called as Uplinks.

i want to understand if the GLC-GE-100FX sfp is compatible in the 24 SFP ports (which we normally configure as access ports).