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Fabricpath CE dot1q trunk

Level 1
Level 1

If ruining fabricpath in a leaf, spine (vpc+ l2/l3 boundary) and l3 core design is it possible to breakout on a classical ethernet dot1q trunk from the spine to temporarily pass the fabricpath vlans to another site (catalyst only)?

4 Replies 4

Steve Fuller
Level 9
Level 9


Yes this is possible, and indeed we're doing something very similar to what you're proposing.

We have Nexus 7K spine switches, which are also the L3 boundary running vPC+, and these are connected via standard IEEE 802.1Q trunks to standard STP capable switches.

The area to be mindful of is that a FabricPath CE (Classic Ethernet) ports behave as if running STP "root guard" and as such will become disabled if they receive a superior STP BPDU e.g., one with a lower priority. You'll see a SYSLOG message along the lines of %STP-2-L2GW_BACKBONE_BLOCK if this occurs.

There's more detail on this in the FabricPath Versus Classical Ethernet Networks section of the Cisco Nexus 5000 Series NX-OS Operations Guide.

The other document on FP that would be worth looking through is Mark Stinnette's Quick Start Guide :: FabricPath. This is a cook book style configuration guide, and some of the "recipes" shown deal with exactly this and need to ensure the FP domain is the STP root.


Hi Steve - Thanks for the reply, very helpful. I spoke with a guy from cisco @ netapp insight who also said this could be done. He told me to look up the slide deck from cisco live which has info on this when migrating from CE into DCB environment.

Just out of curiosity, what line cards do you terminate FP and then route north from? The info I have read states FP > Fxxx > fabric > Mxxx > route north.... However, I believe this can all be done on the F2e cards now?


Our environments pretty old now so we're using the N7K-F132XP-15 for southbound FabricPath and the N7K-M108X2-12L for the northbound routed connections.

The F2E I/O module supports Layer-2 and Layer-3 so in theory this module could be used for both, but I've not looked at the capabilities of the F2E module from a layer-3 perspective.


thanks steve