Table of Contents
Question
An engineer is designing a BGP solution supporting a VXLAN environment over a Layer 3 IPv4 network fabric with these requirements:
- provide Layer 2 adjacency
- allow VM migration of workloads between sites
- IGP is OSPF
Which BGP address family must the engineer choose?
A. L2VPN VPLS-VPWS
B. L2VPN EVPN
C. IPv4 unicast
D. VPNv4
Answer
B. L2VPN EVPN
Explanation
The correct answer is B. L2VPN EVPN. Here is a detailed explanation:
BGP is a protocol that can be used to exchange routing information between different networks, such as autonomous systems (AS). BGP can support different types of network layer reachability information (NLRI), which are encoded in different address families. An address family defines the format and semantics of the NLRI data.
VXLAN is a technology that allows creating overlay networks that extend Layer 2 segments over a Layer 3 network. VXLAN uses UDP encapsulation to carry the original Layer 2 frames over an IP network. VXLAN also uses a VXLAN network identifier (VNI) to identify different overlay networks.
To provide Layer 2 adjacency and allow VM migration of workloads between sites, the engineer needs to use a BGP address family that can carry both the MAC address and the IP address of the hosts in the VXLAN segments, as well as the VNI information. This way, the BGP speakers can learn and advertise the host routes across the Layer 3 network fabric.
The BGP address family that can support this requirement is L2VPN EVPN. L2VPN EVPN is an extension of BGP that can carry Ethernet VPN (EVPN) NLRI. EVPN is a technology that provides Layer 2 VPN services over an IP network. EVPN can also support VXLAN integration, by using a new route type called Ethernet Segment route. This route type can carry the MAC address, the IP address, and the VNI of the hosts in the VXLAN segments.
The other options are incorrect for the following reasons:
- L2VPN VPLS-VPWS is a BGP address family that can carry Virtual Private LAN Service (VPLS) or Virtual Private Wire Service (VPWS) NLRI. VPLS and VPWS are technologies that provide Layer 2 VPN services over an MPLS network. They are not compatible with VXLAN and cannot support the requirements of the question.
- IPv4 unicast is a BGP address family that can carry IPv4 unicast NLRI. This address family can only carry the IP address of the hosts, not the MAC address or the VNI. It cannot provide Layer 2 adjacency or allow VM migration of workloads between sites.
- VPNv4 is a BGP address family that can carry VPN-IPv4 NLRI. This address family is used to support Layer 3 VPN services over an MPLS network. It can carry the IP address and the route distinguisher (RD) of the hosts, but not the MAC address or the VNI. It cannot provide Layer 2 adjacency or allow VM migration of workloads between sites.
Reference
- Cisco Nexus 9000 Series NX-OS VXLAN Configuration Guide, Release 10.2(x) – Configuring VXLAN BGP EVPN [Cisco Nexus 9000 Series Switches] – Cisco
- Layer 2 Configuration Guide, Cisco IOS XE Gibraltar 16.11.x (Catalyst 9300 Switches) – Configuring VXLAN BGP EVPN [Support] – Cisco
- BGP EVPN VXLAN Configuration Guide, Cisco IOS XE Dublin 17.11.x (Catalyst 9300 Switches) – Configuring Additional BGP EVPN Features [Support] – Cisco
- BGP EVPN VXLAN Configuration Guide, Cisco IOS XE Amsterdam 17.3.x (Catalyst 9400 Switches) – Feature History for BGP EVPN VXLAN [Support] – Cisco
Designing Cisco Enterprise Networks ENSLD 300-420 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Designing Cisco Enterprise Networks ENSLD 300-420 exam and earn Designing Cisco Enterprise Networks ENSLD 300-420 certification.