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New Member

Connecting 3750X via fiber

We have four 3750x Ci

sco Switches.  We would like to connect our database server

to the switch via fiber connection. What would we need to purchase to do this?  We have the Cisco 3750x-48T-S.  We do not have any of the additional network modules.

Everyone's tags (2)

Re: Connecting 3750X via fiber

If you are going to interconnect a switch with a RJ-45 UTP connection to server with a RJ-45 UTP connection (via fiber cable), you can purchase a media converter for each connection, which are available from many sources (I have provided one below).

Typical set-up

Switch/UTP interface ---> CAT-x ---> UTP interface/media converter/fiber interface ---> fiber ---> fiber interface/media converter/UTP interface ---> UTP interface/Server

You will need to know the following information:

- Port speed

- Fiber type (multimode or singlemode)

- Distance

- Connector type (easy to order a hybrid jumper to mate with the convertor)

- Managed or unmanaged

OMNITRON Media Converters

Let us know if you have additional questions.Hope this helps!


New Member

Re: Connecting 3750X via fiber

We are actually wanting to connect fiber directly from the server to the switch

- not using RJ45 cabling.  Would we need to purchase the network module with four GBE or two 10 GBE SFP+ interfaces?

Re: Connecting 3750X via fiber

If you are connecting to a GE server port, then you could use either Network Module.  According to the switch data sheet, the 2x 10GbE Network Module can be configured to support up to 4 GE ports (per table below):

Table 3. 10GbE Network Module Configuration

10GbE Network Module

10GbE SFP+ Ports

GbE SFP Ports







The 10GbE module probably is more expensive, but provides some future-proofing if you upgrade the server to 10GbE in the future.

New Member

Re: Connecting 3750X via fiber

Thanks, that is what I thought.  I

then asked our hardware vendor for a quote for 4 10 GBE SFP+ modules.  He responded with

According to Mark, my engineer, you also need the SFP+  Do you know which one you need?

SFP-10G-LR= 10GBASE-LR SFP+ module

SFP-10G-SR= 10GBASE-SR SFP+ module

SFP-10G-LRM= 10GBASE-LRM SFP+ module

SFP-H10GB-CU1M= 10GBASE-CX1 SFP module

SFP-H10GB-CU3M= 10GBASE-CX3 SFP module

SFP-H10GB-CU5M= 10GBASE-CX5 SFP module

I responded ...

According to the documentation that came with the switches the Part #3KX-NM-10G contains the SFP+....

The Cisco Catalyst 3750-X Series and 3560-X Series Switches support an optional network module for uplink ports. The default switch configuration doesn't include the uplink module; the customer has the flexibility to choose from four GbE port (3KX-NM-1G) or two 10GbE port (3KX-NM-10G) network module at the time of switch purchase. The 10GbE uplink module features four physical ports with two SFP+ and two regular SFP ports. The SFP+ interface supports both 10GbE and GbE port, allowing customer to use their investment in GbE SFP and upgrade to 10GbE when business demands change, without having to do a comprehensive upgrade of the access switch. The uplink module is hot swappable. The 10GbE network module can be used in any of the combinations shown in Table 3.

I assumed for the 3750x there were only two options - those listed above.  I'll take a look and let you know.

Am I missing something?

Re: Connecting 3750X via fiber


The Network Module (3KX-NM-10G or -1G) just provides the SFP/SFP+ module slots; you still need to add the SFP optical transceiver module(s).  The selection of the particular optical transceiver module is dependent upon the link speed, link length and link fiber type.

What type of optical interface is on your connected server? You need to match the optical interfaces on the switch port and the server.

Optical transceiver modules do not negociate link speed, so if you need 1GE, you purchase a GE SFP optical transceiver; and if you need 10GbE, you purchase a 10GbE SFP.

New Member

Re: Connecting 3750X via fiber

Interface Type - PCI Express x4

So, I've checked out some ofthe GBIC modules.  Am I correct in assuming the major difference in price is based on the maximum distance?

New Member

Re: Connecting 3750X via fiber

Yes, Wede. You're correct.

Just to your information the name GBIC is not more used. The right term now is SFP (Small Formfactor Pluggable).

You have SFP longwave, shortwave and CWDM that costs something like US$ 3500.00. CWDM are used to very long distances (60 KM). Longwave can be used to distances like 10 KM, 20 KM until 50 KM. It dependes of laser power.

The SFPs are cheaper ones that support smaller distances.

New Member

Re: Connecting 3750X via fiber

Hi Wade.

I have a doubt about your question?

Why do you want to change your current copper connection to a fibre connection? Is it about to have better performance? Is it about an eletromagnetic interference in copper cable?

What kind of protocol you want to use after those changes? Ethernet or Fibre Channel?

If your problem is about performance, you can improve it using a CAT6 copper cable.

If problem is about eletromagnetic interference, you are right to change your connection.

If you want to change protocol to Fibre Channel, you can't keep your switches. You will need a Fabric Switch.

New Member

Re: Connecting 3750X via fiber

We are upgrading our SAN and database server to fiber connections from SCSI.  We are doing this due to a growing number of users and speed issues.  We do not want to upgrade every connection in our environment - just those to and from the SAN and database.

Hall of Fame Super Gold

Re: Connecting 3750X via fiber

If your problem is about performance, you can improve it using a CAT6 copper cable.

Incorrect. Any type of copper cable will have the same exact performances in terms of speed, data transfer rate, etc.

They will have different electrical performances, but that is not of much interest for practical purposes.

If problem is about eletromagnetic interference, you are right to change your connection.

Not said. One can use S-FTP cables to prevent EMI.

New Member

Connecting 3750X via fiber

I have a similar situation here, am using a

WS-C3750X-48P-L switch, but what i need to know is what is the MINIMUM IOS FOR GBIC SUPPORT ?


Connecting 3750X via fiber

Look on the transcevier Compatibility Information page, select the module speed (1GE or 10GE - depending upon the Network Module you are using - Table below) you will be using, then find the hardware part number (WS-C3750X-48P) that the transceiver will be installed in; the table will show you the minimum IOS software required to operate the optical module.   

The WS-C3750X-48P does not have any pluggable interfaces - the Network Modules installed in the switch do.


Four GbE port network module


Two 10GbE SFP+ ports network module with four physical ports with two SFP+ and two regular SFP ports


Two 10GB-T ports network module


Service Module with two 10GbE SFP+ ports network module for Netflow and MACsec encryption

Hope this helps!


Re: Connecting 3750X via fiber

Lets go back to basics

Gig is Gig and it does no difference if you use copper or fiber.(in terms of transfering the data)

If you want to use Fiber, then you will get out of electrical disturbances and grounding problems and such, but it will still only deliver 1 Gig wich is the same as 1 Gig over copper. (same thing as the old question, Wich weights more 1 Kg of feathers or 1 Kg of lead... answer = both weights 1Kg)

so ok you want to use fiber, then you need to buy the network module uplink, I Personally would go for the 3KX-NM-10G.

why ? well since you are able to get 4 normal gig ports OR 2 10 gig ports. the 10 gig ports are maybe not interesting today, but it will most likely be tomorow. and then you are already set for that.

To that module you need to buy a SFP (to plug in to the module and the module plugs into the switch).

That SFP needs to be the same type that the network card supports.

(the network card most likely supports either singelmode or multimode.)

PCI express = the connection to the bus inside the server ie the slot you put the network card in, inside the server.

what does the network card support on the otherside is the magic question.

if the network card supports Singelmode then the SFP needs to be one that can handle single mode.

if the network card supports Multimode then the SFP needs to be one that can handle multimode.

Actually cisco has one SFP that supports both singel AND multimode.

The signal transfer distance is only one of many factors that inflicts on the pricing. so you can not buy a sfp with how much it costs in mind, only what it can support. there are several different types that can support the same distance. ie wavelength (colour of the "laser") and other things.

Buy the correct cabeling with the correct connectors for the fiberoptics.

ok so now you have checked what the network card supports in terms of fiber optics, bought the correct cabeling for connected devices and the cabeling to the switch via the choosen module and correct SFP.

Thats what you need in order to connect your device to the 3750x

now for the bonus question.

Are the 3750x connected in a stack and is it powerstacked ?

if not then I would seriously consider it.

that is one major advantage of the 3750x.

Good link for SFP information

good luck


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