When you run fiber optics and Ethernet, you need transceivers to enable communication across your devices and systems.
When you shop Cisco, you have a lot of options, and for 1000BASE-T transceivers, three models maintain prominence: GLC-T, SFP-GE-T, and GLC-TE. Which is right for your network? Let’s tour all three models to see how they are alike and how they differ so you can make an informed choice.
Let’s start with GLC-T. This is a 1000BASE-T SFP transceiver. It supports standard Category 6 Ethernet. That means unshielded copper, twisted base pairs, and RJ45 connections. It supports 1 Gbps connections with these cables (10/100/1000) at runs of up to 100 meters.
In addition, GLC-T provides auto negotiation and auto MDI or MDIX.
Another point worth highlighting is the COM operating temperature range. For those who don’t have such things memorized, this is a standard commercial performance rating, and COM devices can operate nominally at temperature ranges between 0 and 70 degrees Celsius.
That covers the basic performance of GLC-T, but there’s another issue that is arguably more important. Cisco has been phasing out this specific model. The last new devices were produced in 2017, and the end of service life is fast approaching.
That brings us to SFP-GE-T. In a lot of respects, these transceivers are identical to GLC-T. Both support 1000BASE-T SFP. Both work with standard Cat 6 Ethernet. They provide the same data rates, auto negotiation, and auto MDI/MDIX.
In fact, the only major difference between the two has to do with safe operating conditions. While GLC-T is COM-rated, SFP-GE-T is NEBS 3 ESD EXT rated.
That’s a bit of a mouthful, but NEBS ratings are managed by the Network Equipment Building System. This standard provides three levels of performance, each pertaining to safe operating temperatures and general device durability.
Level three is the highest in the NEBS standard, and that’s the rating applied to SFP-GE-T. There are a number of tests that go into NEBS standards, but there are three specific things you need to know about NEBS 3.
First, it supports nominal operation from temperatures as low as -40℃ to as high as 85℃. So, NEBS 3 devices are much more robust than COM devices.
Second, NEBS also certifies interference minimization. NEBS 3 devices won’t cause interference with your other equipment.
Finally, NEBS 3 is required for some telecommunication applications. Even when it isn’t required, NEBS 3 is chosen by many networking engineers for the most critical systems.
This lifecycle that we keep mentioning is why Cisco developed GLC-TE. It’s the replacement hardware for both GLC-T and GLC-TE. In terms of performance, it’s right in line with the other two transceivers. You can expect the exact same level of performance.
Getting into the key difference, GLC-TE has a different temperature rating from either of the other two. This one is rated for EXT. Skipping the jargon, this means that GLC-TE transceivers operate safely from -5℃ to 85℃. You can see that this splits the difference between the other two temperature ratings, which is why Cisco is comfortable using this single model to replace the other two.
Which Should You Get?
When you compare the hardware for these three models, you see that performance isn’t just similar. It’s identical in most respects. So, which one should you get?
As you’ve already seen, two of the options aren’t really viable anymore, which means in pretty much all applications, you’re best choosing GLC-TE. The good news is that it does not have an announced end of life at this point, so you can expect it to remain in support and service for years.
If you go to the trouble of purchasing GLC-T or SFP-GE-T equipment, they will be completely out of support very soon. They are not savvy investment options.
But, what if you actually need NEBS 3 transceivers? What should you do then?
In that case, Cisco does have a variant of the GLC-TE that can handle NEBS 3 environments. In Cisco literature, it is notated as “GLC-TE-=”. Sometimes, third-party resellers might label it as GLC-TE-I. It is more expensive, so it’s usually best to stick with the standard model for any work that doesn’t specifically need a NEBS 3 rating.
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