Overview: 3550 Series Switches

The Cisco 3550 series is the most cost-effective used option for a true Cisco layer 3 switch. The 3550 series was the first low-price layer 3 switch (roughly $5000 list price new). These switches do most of the typical layer 2 features of modern Cisco switches, plus they support layer 3 forwarding, the configuration of layer 3 switching, and support for a variety of IP routing protocols.

Be careful to avoid the natural mistake of confusing the older Cisco Catalyst 3500XL series switches with the 3550 series. The easiest way to tell the difference between the two is that for 3500XL models, Cisco used the last 2 digits of the main 4-digit product number to identify the number of access ports in that model. For example, the 3500XL series includes models 3524 (24 port) and 3548 (48 port). For the different 3550 series, Cisco names all the 3550 models with exactly “3550” as 4 digits in the name, with additional digits to imply the number of ports – for example, 3550-24. This web page ignores the 3550XL series. Look at the 3550 datasheets for all the 3550 models.

Feature Fact
Popularly sold as new in years: 2000 – 2005
EOS 2005, 2006
Common Replacement: 3560
Original software options: Standard Multilayer Image (SMI)
Enhanced Multilayer Image (EMI)
More recent software: IP Base
IP Services

Cisco Feature Navigator:
Find IOS files by Version, feature set, and platform

3550 Series Software

The original models of the 3550 had two main software branches:

  • Standard Multilayer Image (SMI)
  • Enhanced Multilayer Image (EMI)

Both support layer 3 switching, but only the enhanced image supported EIGRP, OSPF, and BGP.

At later IOS versions, Cisco started using a more router-like feature set convention, with these main four feature sets, with notes about the comparison to SMI and EMI:

  • IP Base (SMI replacement)
  • IP Base with Crypto
  • IP Services (EMI replacement)
  • IP Services with Crypto

Note that while the newer feature sets replaced SMI and EMI, the replacement was not feature-for-feature.

Finally, note that switches purchased from Cisco originally as SMI switches can be upgraded to EMI. In fact, often times eBay listings for 3550’s use wording like “3550 SMI switch with EMI software”.

3550 Series Hardware

3550’s have some number of fixed 10/100 ports, plus some GBIC slots. The following tables lists SMI hardware models that are the lower priced models in the used market. The same models with “EMI” instead of “SMI” have the same hardware, but were shipped from Cisco with the EMI software.

Potentially Popular 3550 SMI Switches

Common name Product Number for SMI 10/100 ports GBIC slots
3550-24 WS-C3550-24-SMI 24 2
3550-24 PoE WS-C3550-24PWR-SMI 24 2
3550-48 WS-C3550-48-SMI 48 2

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