VXLAN BGP EVPN Control Plane: Underlay Connectivity and Route Advertisement
Which TWO statements about VXLAN BGP EVPN control plane are true? (Choose two.)
Quick Answer
The answer is that BGP EVPN advertises MAC addresses and IP addresses as routes, and the VXLAN underlay network provides IP connectivity between VTEPs. The first statement is true because BGP EVPN functions as the control plane for VXLAN, using MP-BGP to distribute MAC/IP address information as Network Layer Reachability Information (NLRI) across the overlay, enabling hosts to be reached without flooding. The second statement is correct because the underlay—typically an IP fabric running OSPF or IS-IS—establishes basic IP reachability between VTEPs, which is a prerequisite for VXLAN tunnel encapsulation and decapsulation. On the Cisco DCCOR 350-601 exam, this concept tests your understanding of how the control plane and data plane interact in modern data center fabrics; a common trap is confusing the underlay’s routing protocol with the overlay’s EVPN route advertisement. Remember the memory tip: “Underlay gets you there; EVPN tells you who is there.”
⚠ Common exam trap
Cisco often tests the distinction between the 24-bit VNI (VXLAN Network Identifier) and the 32-bit VXLAN segment ID used in some older documentation, leading candidates to mistakenly select a 32-bit identifier.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The underlay network provides IP connectivity between VTEPs
The VXLAN underlay network (typically an IP-based fabric using protocols like OSPF or IS-IS) provides IP connectivity between VTEPs, enabling them to encapsulate and decapsulate VXLAN packets. Without this underlay reachability, VTEPs cannot communicate, making it a foundational requirement for VXLAN operation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The underlay network provides IP connectivity between VTEPs
Why this is correct
Underlay routing (e.g., IS-IS, OSPF) enables VTEP-to-VTEP reachability.
- ✓
BGP EVPN advertises MAC addresses and IP addresses as routes
Why this is correct
EVPN Type-2 routes carry MAC/IP information.
- ✗
VXLAN encapsulates Ethernet frames in IP packets using MPLS labels
Why it's wrong here
VXLAN uses MAC-in-UDP encapsulation, not MPLS.
- ✗
VXLAN uses a 32-bit network identifier (VNI)
Why it's wrong here
VXLAN VNI is 24 bits.
- ✗
The control plane is responsible for actual data forwarding
Why it's wrong here
The control plane distributes routes; data plane forwards packets.
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Same concept, more angles
3 more ways this is tested on 350-601
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. In a VXLAN EVPN fabric, which protocol is used to exchange MAC and IP address reachability information among VTEPs?
easy- ✓ A.BGP
- B.IS-IS
- C.EIGRP
- D.OSPF
Why A: In a VXLAN EVPN fabric, BGP (Border Gateway Protocol) is used as the control plane protocol to exchange MAC and IP address reachability information among VTEPs. Specifically, MP-BGP (Multiprotocol BGP) with EVPN address family (AFI L2VPN / SAFI EVPN) carries Type-2 routes (MAC/IP advertisement) to distribute host reachability across the overlay network, enabling efficient MAC learning and ARP suppression.
Variation 2. In a BGP EVPN deployment, route type 2 (MAC/IP advertisement) is used to advertise MAC addresses. What additional information is carried in route type 2 for IP routing?
hard- A.IP address and route distinguisher
- ✓ B.IP address and MAC address
- C.IP prefix and next-hop
- D.MAC address and VNI
Why B: In BGP EVPN, route type 2 (MAC/IP Advertisement Route) is used to advertise both MAC addresses and their associated IP addresses. The additional information carried for IP routing is the IP address and the MAC address, enabling the control plane to support both Layer 2 bridging and Layer 3 routing (e.g., host route advertisement for IP-based forwarding). This is defined in RFC 7432, where the route type 2 NLRI includes a MAC address field and an optional IP address field.
Variation 3. In an EVPN-VXLAN fabric, a network engineer notices that MAC addresses learned from an external router are not being advertised as EVPN type-2 routes. The external router is connected to a leaf switch via a Layer 3 port. Which additional configuration is needed on the leaf switch?
hard- A.Configure `redistribute host-routes` under the BGP address-family l2vpn evpn.
- B.Configure `evpn` under the VLAN interface associated with the external router's VLAN.
- ✓ C.Configure `ip arp evpn` on the Layer 3 interface.
- D.Configure `routing-config` under BGP to enable both MAC-VRF and IP-VRF.
Why C: When an external router is connected via a Layer 3 port, the leaf switch learns the router's MAC address through ARP, not through a VLAN. To advertise this MAC as an EVPN type-2 route, the `ip arp evpn` command must be configured on the Layer 3 interface. This command enables the switch to synchronize ARP entries into the EVPN BGP control plane, allowing MAC/IP advertisement for directly connected hosts on routed interfaces.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-601 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-601 exam.