I'm putting together a SCAPY based tool for simulation. I want to add support for Cisco FabricPath, but I can't find any PCAP's online. My questions are:

  1. What is the expected behavior of Cisco FabricPath in terms of traffic profile? Is it safe to assume that, as an inter-switch L2 protocol, will not be maintained across WAN (MPLS, GRE) links? Is it also safe to assume Cisco FabricPath headers will only be limited to inter-switch traffic?

  2. Is it safe to assume VLAN and VLAN tagged traffic will be maintained within the Cisco FabricPath frame?

I do not have process any Nexus or Cisco equipment that could simulate this.

  • 2
    Never assume you will not see LAN protocols over GRE (or any kind of) tunnels... management requirements override engineering best practices on a daily basis.
    – cpt_fink
    Commented Jul 3, 2014 at 2:56

1 Answer 1


FabricPath transports Ethernet frames. Take a look here for frame format:


If your device/software package is to work between two FP switches, mind you it's not supported today. Also, make no assumptions with regards to what will protocol do or don't do - put a lot of effort in checking if the thing you received matches your expectations and only then act/call some functions.

And yes, VLAN tags are carried through the FP domain if the original traffic was tagged.

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