Topology featuring spine-leaf connections
Topology featuring spine-leaf connections
Hi, I've begun exploring the spine-leaf topology more deeply, but I'm still struggling to grasp the technical details. The biggest confusion comes from all the "No STP" discussions. For simplicity, let's assume I have one server, two leaf switches and two spine switches. Both NICs on the server connect to both leaf switches, while each leaf switch connects to both spine switches. Neither type of switch is directly linked to the other. (Leaf-Leaf or Spine-Spine connections are separate.) So far everything seems clear. What's tripping me up is the mention of implementing this using L3 or L2. Does a Layer 3 setup mean each uplink from leaf to spine operates independently? For instance:
- Leaf1 Port1 connects to Spine1 Port1
- Leaf1 Port2 connects to Spine2 Port1
- Leaf2 Port1 connects to Spine1 Port2
- Leaf2 Port2 connects to Spine2 Port2
This setup avoids STP because broadcasts don't cross network boundaries, eliminating switching loops? And it's even more puzzling how Layer 2 handling works when every leaf switch is linked to every spine switch. I've heard about SPB or TRILL as alternatives to STP—would that mean devices like Ubiquiti EdgeSwitch can't be used for this topology since they don't support SBP/TRILL on Layer 2, and only have limited L3 support? So a L3 approach isn't feasible? Thanks!
Spine and lead represents an advanced architecture for most data centers. Its primary goal is to avoid loops while supporting extensive scalability and redundancy. The structure relies on spine-leaf relationships where nodes are never directly linked, ensuring each node connects with every other node of the opposite type. You might assume this creates loops, but upon closer inspection you won’t encounter a triangle loop. Since spines and leaves aren’t connected, they can’t pass through one another, preventing loop formation. A quick visual of traffic flow between switches shows paths that don’t circle back—traffic may take several routes to reach its destination, but each hop is distinct (red vs green). From an L2 perspective, you won’t need STP because physical loops are absent; everything remains within two hops. Consider the broadcast behavior: even if broadcasts occur, they’re not repeated from the source port since there’s only one uplink channel available. This reinforces loop prevention. For this reason, support for multi-link operation is essential. At the L3 level, approaches differ—routing or switching can be used, and many designs now favor L3 for improved load balancing and redundancy compared to L2. With BGP EVPN/VXLAN deployed at Layer 2, implementing L3 offers better performance and resilience, leveraging multiple uplinks from leaves to spines to ease congestion.
Thanks for your reply! So staying on L2, if my leaf connects to three different spines, those ports would cause a delay on the leaf and a latency increase on the spines? I think this means it's not feasible to form a loop. Regarding L3, I'm not familiar with EVPN/VXLAN, but I found a YouTube series that seems to cover it well according to another source. If you're interested in the video, thanks!
It's been a while since I explored spine and leaf, and I'm struggling to recall the details. From what I understand, MLAG applies to spine structures. Go through VXLAN carefully—it's complex, so make sure you're at least at an intermediate level to fully grasp it. This protocol is really powerful and has many applications beyond just DC. By the way, Network Direction offers excellent video content that breaks down protocol theory; I strongly suggest checking them out.