Jul 24, 2026 · 1 hr 10 min · 12 segments
Shortest Path Bridging (SPB) remains an intriguing and reliable fabric technology, offering a unique approach to Ethernet that differs from more widely deployed fabrics such as EVPN/VXLAN. Jeff Wilson…
Jeff WilsonGuestEthan BanksHost
Drew Conry-MurrayHostUh, another introductory question here: Do I need special hardware to run an SPB fabric?
Again, I don't wanna jump too far ahead in my notes here, but that's one of the distinctions between shortest path bridging and EVPN is the, uh, the merchant silicon really bought into EVPN in a way that shortest path bridging never caught up with.
So you are relegated to specific providers that, uh, with silicon and software support to run SPB.
So, uh, the, the provider-based bridging introduced the ISID, the service identifier, and that's pretty much the isolation, uh, identifier across that backbone.
So any service gets slotted into an ISID, and then that ISID, uh, uh, gets, gets announced from every participant on the edge of the network, and that's how those trees are built.
As a, as a, as a edge node comes up and says, "I have this service available locally," it will announce into ISIS through whatever TLV is appropriate, and then builds the trees from there.
So the, the encapsulation is gonna be a backbone source address, a backbone destination address, a backbone VLAN ID, and the ISID, and those get wrapped around the customer MAC.
As soon as the edge bridge receives the packet, it has the entire topology available and can make a routing decision.
You go to that edge port over there, so it assigns that destination address for that edge bridge, and the rest is just switching across the fabric underlay.
I think we mentioned in the introduction it's basically Extreme these days that's selling a platform that supports SPB.
Uh, another introductory question here: Do I need special hardware to run an SPB fabric?
Again, I don't wanna jump too far ahead in my notes here, but that's one of the distinctions between shortest path bridging and EVPN is the, uh, the merchant silicon really bought into EVPN in a way that shortest path bridging never caught up with.
So you are relegated to specific providers that, uh, with silicon and software support to run SPB.
So, uh, the, the provider-based bridging introduced the ISID, the service identifier, and that's pretty much the isolation, uh, identifier across that backbone.
So any service gets slotted into an ISID, and then that ISID, uh, uh, gets, gets announced from every participant on the edge of the network, and that's how those trees are built.
As a, as a, as a edge node comes up and says, "I have this service available locally," it will announce into ISIS through whatever TLV is appropriate, and then builds the trees from there.
So the, the encapsulation is gonna be a backbone source address, a backbone destination address, a backbone VLAN ID, and the ISID, and those get wrapped around the customer MAC.
As soon as the edge bridge receives the packet, it has the entire topology available and can make a routing decision.
You go to that edge port over there, so it assigns that destination address for that edge bridge, and the rest is just switching across the fabric underlay.
I think we mentioned in the introduction it's basically Extreme these days that's selling a platform that supports SPB.
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