Data Center Routing and Overlay Networking
This domain covers EVPN route types, VXLAN encapsulation, MAC-VRF versus IP-VRF, route targets and route distinguishers, symmetric versus asymmetric IRB, and MAC mobility.
EVPN route types
- Type 1, Ethernet A-D: per ESI (and per Ethernet tag), used for aliasing and fast convergence.
- Type 2, MAC/IP: MAC reachability plus an optional IP for ARP/ND suppression; carries the MAC mobility extended community.
- Type 3, IMET: inclusive multicast per VNI, telling peers where to send BUM traffic via ingress replication or multicast.
- Type 4, Ethernet Segment: identifies the multihomed segment and its originating PE.
- Type 5, IP Prefix: carries IP prefixes, used for symmetric IRB and external/default routes.
Encapsulation and VRFs
- VXLAN uses outer IP/UDP with destination port 4789 and a 24-bit VNI; the VTEP source is the loopback, so MTU must be about 1600 or larger.
- MAC-VRF maps a VLAN to a VNI (
set vlans v100 vxlan vni 10100); IP-VRF is a routing instance with a Layer 3 VNI. - Symmetric IRB gives each leaf a Layer 3 VNI per VRF; asymmetric IRB relies on IRB interfaces on every leaf with no Layer 3 VNI.
Worked example
VLAN 100 maps to VNI 10100 on leaf1 and leaf2. Configure set switch-options vtep-source-interface lo0.0, set switch-options vxlan vni 10100? No: the VNI lives under the VLAN, and the import/export policy lives under set protocols evpn vni-options vni 10100 vrf-target target:65000:10100. If leaf2 uses a different target, Type-2 routes arrive but are never imported.
Traps
- Route target mismatch: routes appear in
show route table bgp.evpn.0but not inshow evpn database. - VNI mismatch between leaves: the control plane looks healthy while the data plane drops encapsulated frames.
- Expecting Type-2 routes to carry subnets; prefix advertisement needs Type-5.
- Duplicate static MAC entries that trigger endless MAC mobility moves and dampening.