HN835: The Pros and Cons of Shortest Path Bridging (SPB)

Ethan Banks (0:00)

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That's meter.com/heavynetworking to book a demo. In March 2026, Drew and I attended Xtreme Networks Connect event in Orlando, Florida wearing our industry analyst hats. And at that event, we caught up with Xtreme executives and product managers about Xtreme's perspective on how to build networks. And a cornerstone of the Xtreme point of view is Xtreme Fabric. Now, Xtreme Fabric came out of the acquisition of Avaya years ago, and that fabric is intriguing because it has a reputation for being easy to use and reliable. But it's not like other fabrics you might have heard of. It's not based on EVPN, Vxlan, like so many are in 2026 Instead, it's based on Shortest Path Bridging. SPB is a standard that's made its way into production in a number of use cases. But if you've never run it before, it's different.

I am Ethan Banks, along with Drew Conray-Murray. And if you like to keep up with industry events, news and the occasional meme, follow us on LinkedIn. Our guest today is Jeff Wilson. Jeff's the network architect who's hands on with Shortest Path Bridging. We're going to chat with Jeff about SPB to demystify it, understand how it moves packets around the network, and ponder whether or not SPB in 2026 is a technology that solves problems you have in your network. And if you heard me say all these things about Xtream, is this a sponsored show by Xtream? Not in this case. Xtream might be coming on board as a sponsor. We've been chatting with them, but that is not this show. Jeff is just someone who we ran into, knows SBB, has worked a little bit with Xtream, and so here he is to chat with us. So Jeff, welcome to Heavy Networking. In a sentence or two, would you tell the nice people out there who you are and what you do?

Jeff Wilson (2:03)

Well, good morning, Ethan, Drew. It's morning here anyway. Thanks for having me on the show. Happy to be here. I'm more or less a network architect with about 20 years of production infrastructure ownership from design through operations.

I have some SBBM work. I designed a 40-node fabric for a medium-sized private university. Most recently, I built some automation tooling around the ISIS control plane to surface topology that LLDP couldn't even see.

And that was in support of a brownfield migration off of Avia era SBBM.

Ethan Banks (2:41)

Okay. You said SBBM and we're going to distinguish what SBBM is versus other flavors of SBB at some point here. Let's start even further back than that, further away.

So let's assume everybody listening here, let's assume no one is familiar with SBB, but they know Ethernet and they know IP routing pretty well, Jeff. How would you introduce SBB to that person?

Jeff Wilson (3:03)

It's a lid flipper. So, I mean, you're accustomed to maybe flood and learn where you, just standard Ethernet as you track the source MAC, as on ingress and you learn some kind of forwarding database from that. But SBB takes a different approach. It grew out of the predecessor, which was provider backbone bridging, and that got its IEEE standard was 802.1 AH, Alpha Hotel back in 2008 And that was an extension of Ethernet trends already taking shape across many carriers.

Now, similar to the VNI that you get in Vxlan, the ISID in SBBM moves the namespace from 12 bits to 24 bits. So you've pretty much squared 4K into 16 millionish, right? So the backbone of SBB is the equal cost trees. And that's how SBB solves the hardest problem first, which is multicast. And it builds every other distribution on top of that same tree structure.

Ethan Banks (4:16)

OK, equal cost trees. So you're saying the forwarding paradigm, how SBB moves traffic from node to node, switch to switch, from source to destination. Is it builds some kind of a tree between those two endpoints, or is it more, I don't know?

Jeff Wilson (4:39)

So it, ISIS, it does routing. So rather than learning kind of on the fly based on ingress packets, this is now, we're just talking.

So you got overlay underlay, like you would with any fabric. So I'm just talking about the underlay. I've got the underlay. So the underlay, the way the different bridges learn about each other is through ISIS over layer two connectivity.