Presenter mode

EVPN-VXLAN leaf-spine overlay

Full page · Paths

Walkthrough

Intra-subnet L2 over VXLAN

Same-subnet hosts on different leaves bridge on an L2 VNI. Spines carry underlay IP between VTEP loopbacks; they need not terminate EVPN in an ERB design.

Step 1 / 3
Spine 1 · underlayunderlay transitSpine 2 · underlayLeaf 1 · VTEPVTEP / NVELeaf 2 · VTEPLeaf 3 · VTEPHost A · subnet 10Host B · subnet 20Host C · subnet 10

Leaves are VTEPs (NVEs): they encapsulate/decapsulate VXLAN and speak EVPN. Spines provide underlay reachability between VTEP loopbacks — lean IP in many ERB designs.

Walkthrough

Asymmetric IRB (inter-subnet)

Ingress leaf routes into the destination L2 VNI; the egress leaf only bridges. RFC 9135 warns that participating PEs need remote host ARP/MAC state and MAC-VRF/IRB for all relevant subnets.

Step 1 / 3
Spine 1 · underlaySpine 2 · underlayLeaf 1 · VTEPLeaf 2 · VTEPLeaf 3 · VTEPHost A · subnet 10subnet 10Host B · subnet 20subnet 20Host C · subnet 10

Host A (subnet 10) reaches Host B (subnet 20). Asymmetric IRB: the ingress PE routes the packet into the destination subnet’s L2 VNI so the egress PE can bridge only.

Walkthrough

Symmetric IRB (inter-subnet)

Ingress routes into a tenant L3 VNI; egress routes then bridges. Uses Router’s MAC extended community and a dedicated L3 VNI per tenant VRF (RFC 9135 / Juniper Type-2 symmetric).

Step 1 / 3
Spine 1 · underlaySpine 2 · underlayLeaf 1 · VTEPIRB + L3 VNILeaf 2 · VTEPIRB + L3 VNILeaf 3 · VTEPHost A · subnet 10Host B · subnet 20Host C · subnet 10

Same Host A → Host B intent, symmetric IRB: both ingress and egress PEs perform routing. The tunnel is IP-VRF to IP-VRF via a tenant L3 VNI.