A colleague of mine pointed something out the other day: the numbers and letters that make up the Nexus 2000 (FEX) model actually have meaning! No, I haven't been living under a rock. I think it's pretty clear that with a model number like "2248TP-E" the "22" indicates this is the 2200 series FEX and the "48" indicates it's got 48 ports. But what about the letters that follow the numbers?

The letters have a logic behind them as well. By interpreting the numbers and letters together you can understand exactly how a given FEX is equipped.

Platform series No. User facing ports Port type
(user facing)
Port type
(network facing)
"Enhanced" indicator
2 2 4 8 T P - E

An explanation of each field:

  • Platform series: As of this writing, this is either 21 (first-gen FEX) or 22 (latest gen). I'll save the differences between the generations for another post.
  • User facing ports: The number of ports that downlink to end devices (servers, appliances, etc). This number does not include the number of network/uplink ports. Remember: a FEX must be uplinked to a parent 5500/7000 and this uplink must occur on the dedicated network ports on the FEX.
  • Port type (user): This letter indicates the type of port that is present for downlinking to end devices. The FEX can be ordered with different port types depending on the needs of the network.
    • T - Twisted pair (RJ45 connectors)
    • P - SFP+
    • X - 10GBASE-KR (ie, traces on a backplane/midplane)
  • Port type (network): This letter indicates the type of port that is present for uplinking to the parent switch.
    • P - SFP+
    • Q - QSFP (40Gig)
    • M - Uplink module
    • F - Indicates the FEX comes with some number of Fabric Extender Transceivers (FETs). The FEX itself will be equipped with SFP+ ports.
  • Enhanced indicator: Indicates an enhanced version of the 2200 (bigger buffers, etc)

Some examples:

  • 2248TP-E - 48 ports of RJ45 (T) for hosts, SFP+ (P) ports going north, enhanced model (E)
  • 2232PP - 32 ports of SFP+ (the first P) for hosts, SFP+ for uplink (second P)
  • 2224TF - 24 ports of RJ45 (T) for hosts, SFP+ ports for uplink and comes with FETs (F) for making the physical connection to the parent switch

That's that. With this cheat sheet you should be able to figure out at a glance how a particular Nexus 2000 is outfitted.

Disclaimer: The opinions and information expressed in this blog article are my own and not necessarily those of Cisco Systems.