What is inside an EVPN type 2 route, and what does a remote leaf do with it?
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It carries the RD, the ESI, an Ethernet tag, the host MAC and optionally its IP, a label for the L2VNI and, for symmetric IRB, a second label for the L3VNI. Extended communities add the route targets, the encapsulation type (VXLAN), the advertising leaf's router MAC, and a MAC mobility sequence number after a move. The remote leaf imports it by route target: the MAC goes into the MAC table pointing at the VTEP, the IP becomes a /32 host route in the tenant VRF, and the binding fills the ARP suppression cache.
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Fields, with example values
| Field | Example | Meaning |
|---|---|---|
| RD | 10.0.0.11:32777 | Makes the route unique per leaf and MAC-VRF |
| ESI | 0 | Zero for a single-homed host |
| Ethernet tag | 0 | Zero for VLAN-based service |
| MAC | 0050.56a1.0011 | The host |
| IP | 10.10.10.11 | Optional, learned from ARP or ND |
| Label 1 | 10010 | L2VNI, for bridging |
| Label 2 | 50001 | L3VNI, for routing (symmetric IRB) |
| Route targets | 65000:10010, 65000:50001 | Import into MAC-VRF and IP-VRF |
| Encapsulation | VXLAN (type 8) | Data plane to use |
| Router MAC | the leaf's MAC | Inner destination MAC for routed packets |
Two routes per host
Leaves often send a MAC-only route and a MAC+IP route for each host. The first is enough for bridging. The second drives routing and ARP suppression.
What the receiver installs
- MAC table:
0050.56a1.0011in VLAN 10, next hop VTEP 10.0.1.11, VNI 10010. - VRF table:
10.10.10.11/32via 10.0.1.11, VNI 50001, inner destination MAC set to that leaf's router MAC. - ARP suppression cache: 10.10.10.11 is at 0050.56a1.0011.
They will ask next
Why does the remote leaf need the router MAC?
In symmetric IRB a routed packet travels in the L3VNI as an Ethernet frame. Its inner destination MAC must be the egress leaf's router MAC so that leaf routes it instead of bridging it.
Traps
- Saying the IP field is mandatory. It is optional; MAC-only routes are normal.
- Thinking a type 2 route sets up a tunnel. VXLAN tunnels are stateless.