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November 17, 2023

SFP Modules When Buying or Selling Used Network Equipment

As networking speeds have grown dramatically over the past decade or so, SFP modules have become a critical component in communication networks. They were born in the early days when optical ports were added to equipment. Back then with the cost of an optical port being many times that of a copper port you wanted to only pay for the optical ports you needed but you also had to try to future proof for expansion and you wound up paying a chunk of money for optical ports you may not use for some time. This was the birth of the SFP standard that would allow you to add ports when needed and gave the OEMs the flexibility of offering additional ports which can be “paid for” when they are finally needed by the end user.

Over the years since the SFP port has become the dominate port for optical interfaces on networking equipment. With that popularity has come the competition of multiple vendors supplying the SFP modules. While there are industry standards for these modules that will assure some degree of compatibility for things such as wavelength, distance, fiber type and data rate, there are some issues that can cause modules not to work. The SFP standard calls for a feature called Digital Diagnostic Monitoring. It allows the module to send data to the network equipment providing data about the operation of the module. It enables users to monitor parameters of modules, such as optical output power, input power, temperature and voltage in real time. The standard also defines in the EEPROM a user defined data field where the manufacturer can put any information they want in that field. Unfortunately some manufacturers have used that to determine if the module came from the OEM and if not, the systems flags the module as incompatible even though it is a fully operational module.

The Big Concern: Compatibility

Since the used networking equipment you are looking to buy or sell may come with either the OEM SFP modules, third party modules or even a combination of both.  What you need to do with the SFP modules you have with your equipment will depend upon whether you are buying or selling:


You may think that you can take the SFP modules out of the networking equipment and sell them separately gaining additional revenue for your sale. Actually just the opposite is true as the potential buyer now assumes the risk of which third party module may work with the equipment. They could purchase the OEM module but that will be at a cost that far outweighs the gains of selling the modules independently. Having additional spare modules also increases the selling price of your equipment as it offers compatibility as well as future expansion.



Ideally when buying used network equipment it would have the SFP modules that you need for your current bandwidth needs as well as for some future expansion. So what happens when you determine that you will be needing additional SFP modules to complete your network. You can certainly buy OEM modules but that can come with as much as a 10x price difference to third party modules. Hopefully if your equipment does already have third party modules you should be able to purchase more of the same with low risk of compatibility issues. If you have all OEM modules there are third party SFP modules offered where the manufacturer guarantees compatibility with the OEM equipment.


Network Equipment Coding

If you find your third party SFP  modules “incompatible”, it could be because the OEM is looking for a code in the module that identifies the module as coming from the OEM. Some of the major network equipment manufacturers like Cisco/HP/Aruba did this as a guarantee of performance as they know modules they supply have been fully tested to their network requirements. This alleviates the issue of who is responsible when there is a problem with the link. The OEM will be quick to point the finger at the third party module as the cause of the issue.

Yet they have bowed to pressure from their customers not wanting to pay exorbitant prices by allowing the network card to be set to support these modules. On Cisco platforms the command “service unsupported-transceiver” is generally available in NxOS and IOS versions. The command won’t autocomplete and, as is implied, it is unsupported but allows the use of 3rd party optics but again they will be quick to point at that module when service is required. There is a workaround in that many network operators will successfully use third party modules in their network but keep a few OEM modules in case there is a problem with the link. Since the SFP modules are hot swappable they can swap in the OEM module to determine if the third party module is indeed the problem with the link.

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Navigating the complexities of SFP module compatibility requires understanding the nuances of both OEM and third-party products. Compatibility issues can often be mitigated through careful selection of third-party modules from reputable manufacturers who emphasize quality control and compatibility testing. Companies like FS,com and Advance Technology Solutions can help you navigate the SFP module performance and cost analysis. Balancing cost, performance, and compatibility is key to ensuring a reliable and efficient network infrastructure. So when you are ready to buy or sell networking equipment, a company like TeleTraders is ready along with the SFP support companies we noted here to get you the greatest return on your networking investment or help keep your budget in tack by purchasing used equipment.

About the Editorial Staff

The Editorial Staff at TeleTraders, led by IT asset expert Clay Beckham and his seasoned team, boasts over 10 years of industry experience in IT asset management, secure IT asset disposal, and technology solutions. Founded in 2013, TeleTraders quickly became a trusted source of IT expertise. The team at TeleTraders demonstrates its commitment to excellence, spending countless hours each day handling a wide spectrum of IT equipment, spanning from intricate networking gear to precision barcode scanners. Our team strives to transfer our hands on knowledge into resources for IT professionals in businesses of any size.

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