ACSP EVPN-VXLAN and Network Virtualization 2 — Questions and Answers
Question 1: Which EVPN route type carries MAC/IP advertisement information for individual host reachability?
- Type-1 (Ethernet Auto-Discovery Route)
- Type-2 (MAC/IP Advertisement Route) (Correct answer)
- Type-3 (Inclusive Multicast Ethernet Tag Route)
- Type-5 (IP Prefix Route)
Correct answer: Type-2 (MAC/IP Advertisement Route)
EVPN Type-2 routes carry MAC address bindings (and optionally IP address bindings), allowing VTEPs to learn remote host reachability without flooding.
Question 2: What is the key functional difference between EVPN Type-2 and Type-5 routes?
- Type-2 carries MAC/IP host bindings within a VNI; Type-5 carries IP prefix routes for inter-subnet and external routing (Correct answer)
- Type-2 is used for underlay routing; Type-5 handles overlay tenant routing
- Type-2 carries multicast group membership; Type-5 handles BUM traffic replication
- Type-2 supports IPv4 only; Type-5 supports both IPv4 and IPv6
Correct answer: Type-2 carries MAC/IP host bindings within a VNI; Type-5 carries IP prefix routes for inter-subnet and external routing
Type-2 routes advertise individual host MAC/IP bindings within a Layer 2 VNI, while Type-5 routes advertise IP prefixes (subnets) for inter-subnet routing and external prefix distribution.
Question 3: How does EVPN ARP suppression improve efficiency in VXLAN overlay networks?
- It blocks all ARP traffic between different tenant networks
- It enables VTEPs to answer ARP requests locally using cached MAC/IP bindings learned via EVPN (Correct answer)
- It converts ARP broadcasts to IGMP multicast queries for distribution
- It replaces ARP entirely with Neighbor Discovery Protocol for all tenants
Correct answer: It enables VTEPs to answer ARP requests locally using cached MAC/IP bindings learned via EVPN
EVPN ARP suppression allows VTEPs to respond to ARP requests locally from their MAC/IP binding tables populated by EVPN Type-2 routes, eliminating unnecessary BUM traffic flooding across the fabric.
Question 4: What is an IRB (Integrated Routing and Bridging) interface in an EVPN-VXLAN deployment?
- A dedicated physical uplink interface for inter-VRF routing
- A virtual Layer 3 interface that performs both bridging within a VNI and routing between VNIs/subnets (Correct answer)
- A management-plane interface used to configure the VXLAN control plane
- A redundant interface used by VTEP pairs for active-standby failover
Correct answer: A virtual Layer 3 interface that performs both bridging within a VNI and routing between VNIs/subnets
An IRB interface acts as both the default gateway for hosts within a VXLAN segment and the routing interface for inter-subnet traffic, combining bridging and routing in one logical interface.
Question 5: In a symmetric IRB model for EVPN-VXLAN, how is inter-subnet traffic forwarded between VTEPs?
- Traffic is routed only at the ingress VTEP and then bridged to the egress VTEP
- Traffic is routed at both the ingress and egress VTEPs using a dedicated Layer 3 VNI (Correct answer)
- Traffic is bridged end-to-end without any routing occurring in the fabric
- Traffic is forwarded to a centralized routing controller that makes all forwarding decisions
Correct answer: Traffic is routed at both the ingress and egress VTEPs using a dedicated Layer 3 VNI
In symmetric IRB, both the ingress VTEP and egress VTEP perform routing using a shared L3 VNI, distributing the routing load symmetrically and enabling consistent traffic paths.
Question 6: What is the function of a BGP Route Distinguisher (RD) in EVPN?
- To encrypt EVPN routes during BGP advertisement between VTEPs
- To make EVPN routes globally unique in the BGP table when the same prefix exists in multiple VRFs (Correct answer)
- To set the administrative distance of routes learned via EVPN
- To indicate which VNI is directly associated with a specific BGP EVPN route
Correct answer: To make EVPN routes globally unique in the BGP table when the same prefix exists in multiple VRFs
An RD is prepended to EVPN routes to make them globally unique in the BGP table, allowing identical prefixes from different VRFs or tenants to coexist without ambiguity.
Question 7: In traditional VXLAN without EVPN (flood-and-learn mode), what mechanism handles BUM (Broadcast, Unknown unicast, Multicast) traffic?
- Statically configured ingress replication lists or multicast groups on each VTEP (Correct answer)
- BGP EVPN Type-3 routes advertising VTEP membership per VNI
- OSPF flooding redistributed into the overlay network
- Unicast encapsulation of all BUM traffic to a centralized SDN controller
Correct answer: Statically configured ingress replication lists or multicast groups on each VTEP
Without EVPN, traditional VXLAN relies on either IP multicast groups in the underlay or statically configured head-end replication lists to flood BUM traffic to all VTEPs in a VNI.
ACSP EVPN-VXLAN and Network Virtualization 2
Which EVPN route type carries MAC/IP advertisement information for individual host reachability?