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JNCIE-DC: EVPN-VXLAN Fabric Configuration

JNCIE-DC · Work through your exam, one topic at a time.

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EVPN-VXLAN Fabric Configuration

Domain 2 is the configuration core: turning a working underlay into a tenant-carrying VXLAN fabric with BGP EVPN as the control plane.

Building blocks

  • A routing instance of instance-type evpn holding the bridge domains, with route-distinguisher unique per VTEP (commonly loopback:vni) and vrf-target shared by every leaf that must join the same tenant.
  • protocols evpn encapsulation vxlan, extended-vni-list all, and switch-options vtep-source-interface lo0.0 under that instance.
  • Per bridge domain: vlan-id, vxlan vni, and the access interface under protocols evpn interface.

Route types you must read fluently

Type 1 Ethernet Auto-Discovery (per ESI; aliasing and mass withdraw), Type 2 MAC/IP (MAC reachability and ARP/ND suppression), Type 3 Inclusive Multicast Ethernet Tag (BUM, carries the originating VTEP address), Type 4 Ethernet Segment (multihoming and DF election), Type 5 IP Prefix (routed L3 VNI and DCI).

Worked example

Two leaves, VLAN 100 mapped to VNI 100, RD 10.0.0.1:100 and 10.0.0.2:100, both with vrf-target target:65000:100. The IRB is 10.1.100.1/24 on both with a shared virtual-gateway MAC. A host on Leaf1 ARPs for the gateway and gets a local reply; when it pings a host on Leaf2, Leaf1 looks up the Type 2 route, encapsulates to Leaf2's VTEP loopback, and Leaf2 decapsulates into VLAN 100. Verify with show evpn database, show evpn instance extensive, show ethernet-switching table.

Traps

Mismatched VNI between vxlan vni and the remote leaf, an RD duplicated across leaves, omitting extended-vni-list all so a VNI never gets signaled, forgetting protocols evpn interface on the access port, and assuming data-plane flooding will cover a missing Type 3 route.