MPLS P-Router, Router or Layer-3 Switch?

One of my readers is struggling with the aftermath of marketing gimmicks:

We will implement a new network soon, and we're discussing P-routers versus regular routers versus switches. I'm looking for arguments to go one way or the other.

TL&DR: there’s no difference between router and L3 switch.

The critical part is the functionality you need. Based on their intended use, some boxes tend to have low table sizes (you can’t pump a full BGP table into a ToR L3 switch even though it runs BGP unless you’re David Barroso – more about that in an upcoming Software Gone Wild podcast), or limited QoS, or no shaping, or…

You should always start with “what services do I want to offer”, continue with “how would I best implement them with the simplest possible design”, go down the path of “which functions do I need to make this design work” and finally “which boxes from which vendors fit my needs?

As for MPLS, do keep in mind that very few L3 switches support MPLS, and even those that do tend to have a very limited number of MPLS labels (although QFX5100 does an excellent job squeezing 16K labels out of Trident-II chipset), which might or might not be a problem depending on what the outcome of the previous paragraph is.

Need to Know More About MPLS?

Explore my MPLS/VPN books, and Enterprise MPLS and MPLS Essentials webinars.


  1. If you're a Cisco environment. Look into Cisco EVN for similar MPLS functionality. You won't get the complete feature set of MPLS, but it can help with certain use cases.
    1. Features are supported in IOS XE and IOS 15.0 and above. So it is limited to certain switches as well. But a wider range than MPLS.
  2. You have given some important links about MPLS before now I just knew that by MPLS I can just give labels to data packets but you have discussed some important things about it…
  3. I think its better to go with routers if you can. That way you're not stuck trying to implement features on a switch that does not support them.
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