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Difference between GBIC and SFP module

when its best to use GBIC and When to use SFP ?

what i know is basically SFP is a smaller version of GBIC but I am not clear when to use what any special recommendation ?

Tarun Lohumi
Cisco Employee

GBIC - Datasheet definition:

The industry-standard Cisco Gigabit Interface Converter (GBIC) is a hot-swappable input/output device that plugs into a Gigabit Ethernet port or slot, linking the port with the network. Cisco GBICs can be interchanged on a wide variety of Cisco products and can be intermixed in combinations of 1000BASE-T, 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-ZX, or 1000BASE-CWDM interfaces on a port-by-port basis.

SFP - Datasheet definition:

The industry-standard Cisco® Small Form-Factor Pluggable (SFP) Gigabit Interface Converter is a hot-swappable input/output device that plugs into a Gigabit Ethernet port or slot, linking the port with the network (Figure 1). SFPs can be used and interchanged on a wide variety of Cisco products and can be intermixed in combinations of 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-ZX, or 1000BASE-BX10-D/U on a port-by-port basis.

Ok, now if you have a look at the above datasheets for GBIC's & SFP's, you would find that GBIC & SFP are different in there sizes, hence it is more of a question as to which gigabit solution your device supports. If your device supports GBIC, like 4500's, you will have to go for a GBIC, & if your device supports SFP, like 3750's, you will have to go for a SFP. These days all the latest devices would have SFP's normally.

Also, here is a very good document which lists almost all the GBIC's & SFP's & the devices on which they are supported, you may check your device on this list & decide which one can you use accordingly.

Hope that helps !!

Hi guys, I am having a question... Is the WS-G5484 (GBIC module) able to operate with a GLC-SX-MMD (SFP module) over tha same Fiber? Both are for Multimode fiber and operate at 850nm.

Thanks in advanced.

Yes, you can mix and match.  Just be sure you consistently use gbic or sfp that match the fiber size/type.  Any mismatches in the chain, and you won't get a connection

(although in a lab environment, sometimes you CAN get away with using a 1 or 2-meter Multimode fiber between SingleMode endpoints, but not reliably).

Sushil Kumar Katre
Rising star

Hi Manish,

As pointed in the earlier post the difernce between SFP and GBIC is in the size.

GBIC came into existance before SFPs mostly for fiber connectivity.

The fact was because of big size of GBIC it was not feasible to provide more number of interfaces on a line card or a switch since it occupies more space. In order to resolve this issue people came up with SFPs which were smaller in size hence you can have more interfaces on the same line card or switch as compared to GBICs.

Let's tak an example, have you ever heard of a 48 port GBIC line card on 6500 switch. The answer is no, because its not feasible to have 48 big GBIC interfaces on the form factor of the line card. But a 48 port SFP line card does exists.

Coming to the point when to use what, actually depends on the line card or the switch you are having. Usually [not always], the line cards and switches comes with empty GBIC or SFP slots where you need to purchase the GBIC or SFP modules separately and insert in those empty slot, just like a 6500 chassis which comes with empty slots and you purchase line cards.

Thus if you already have a switch or line card which has GBIC slots you have to use GBICs, simply because SFPs won't fit in and vice versa.

Another case whrere you don't have a switch or line card and want to make a decision whether to use a GBIC or SFP will actually depend on the number of interfaces required and availability of the switches and line cards specific model.

For ex, if you want two fiber interfaces on a line card on 6500 switch, you won't go for a 48 port SFP line card, instead you'l use a 2 port GBIC line card which is available. If you need some 24 fiber interfaces you won't use a 16 [or 18 not sure] port GBIC line card, you'll use a 48 port SFP line card.

Hope this clarifies.

-> Sushil

Hi Sushil

Thanks for the best answer!!!!!!what a good explanation.

Hi sushil

can u explain me about SFM card type also

like u explain between GBIC and SFP

Many thanks


Very best ANSWER!!!. COOL!!!


8 years old but an absolutely great explanation.


i'm also have the same confusion about when i can use GBIC and when i have to use SFP and whats the technical difference between them, as if there is no technical difference except module size then why SFP's had been manufactured.?

You "have to use" GBIC transceivers with GBIC ports and SFP transceivers with SFP ports.

The two will inter-operate across a fiber link (assuming they both support the same fiber standard).

As to why SFPs have been manufactured, Sushil's post answers that with size, although manufacturing cost and power consumption are likely factors too.

With the size of a GBIC, it would be difficult to manufacture 24-port or higher fiber blades - you just can't fit that many GBICS onto the front panel of, say, 4500 or 6500 family switch blade - while 24-port SFP modules (even 48-port models) are available.