Arista VXLAN and EVPN Overview

Question 1

VXLAN

Answer 1

Virtual Extensible LAN

Question 2

VTEP

Answer 2

VXLAN Tunnel Endpoint

Question 3

VNI / VNID

Answer 3

VXLAN Network Identifier

Question 4

BUM Traffic

Answer 4

Broadcast, Unknown Unicast, Multicast Traffic

Question 5

HER

Answer 5

Head-End Replication

Question 6

Intra-data center deployments started moving to Layer 3 to accommodate what three goals?

Answer 6

• accommodate growth
• reduce the blast radius of maintenance or outages
• provide some level of segmentation

Question 7

Intra-data center deployments then frequently ran into a need to extend Layer 2 over the Layer 3 infrastructure to provide Layer 2 adjacencies for application needs such as?

Answer 7

• application clustering
• keepalives
• link local multicast

Question 8

Primary purpose is to establish IP
reachability between VTEP loopback
addresses. 
Leverages the Global Routing Table
(VRF Default).
No tenant (VRF) prefixes should ever
exist within the \_\_\_\_\_.
Arista recommends BGP peering in the
IPv4 unicast address-family to
establish reachability between VTEP
loopbacks.

Answer 8

Underlay

Question 9

Primary purpose is to provide services to
tenants (L2VPN, L3VPN) via VXLAN.
Leverages BGP Peering in the EVPN
Address-Family.
All tenant reachability information exists in
the overlay EVPN control-plane.
Underlay prefixes (such as Loopbacks)
should not exist within the overlay
control-plane.

Answer 9

Overlay

Question 10

What does UDP stand for?

Answer 10

User Datagram Protocol

Question 11

What are the two types of interfaces that VTEP uses and which ways do they face?

Answer 11

• IP interfaces which face the L3 side

- LAN interfaces which face downstream on L2 side

Question 12

What does CAM stand for and what is its functionality?

Answer 12

Content Addressable Memory, it is a system memory construct used by ethernet switch logic. This stores information such as MAC addresses available on physical ports with their associated VLAN parameters.

Question 13

Where typical L2 networks would associate a destination MAC address with an interface, what does VXLAN allow us to attach a MAC address to?

Answer 13

IP address on the other side of a L3 tunnel, specifically the IP address of the VTEP on the other side.

Question 14

What type of encapsulation method does VXLAN use?

Answer 14

MAC-in-IP/UDP encapsulation

Question 15

What does the MTU (maximum transmission unit) have to be increased by in the L3 fabric?

Answer 15

50B, or 54B if Dot1Q header is included

Question 16

How is unicast traffic handled to a remote host once it has been learned by the local VTEP in the context of the “Flood and Learn” concept?

Answer 16

It will be unicast to the remote VTEP (the original source of the multicast signal). Both will update their CAM tables with this destination information

Question 17

The name for an ethernet frame with a payload greater than the standard MTU of 1,500 bytes

Answer 17

Jumbo frame

Question 18

Which behavior can be prevented when using VXLAN with EVPN?

Answer 18

Flooding ARP requests to all VTEPs

Question 19

Describe the VXLAN header, breaking it down by bytes

Answer 19

1B for flags, 3B for VNIs, 4B are reserved for 8B in total

Question 20

Where do the default gateways live in a Leaf-Spine architecture?

Answer 20

Leaf switches

Question 21

How does VXLAN natively perform control plane operations?

Answer 21

Flood and learn

Question 22

What BGP configuration is added to the spine switches in a leaf-spine EVPN architecture?

Answer 22

Configuring our switches to be route reflectors