Deployment Guide

17 Leaf-Spine Deployment and Best Practices Guide | Version 1.0

6 Layer 3 configuration planning

6.1 BGP ASN configuration

When EBGP is used, an autonomous system number (ASN) is assigned to each switch. Valid private, 2-byte

ASNs range from 64512 through 65534. Figure 11 shows the ASN assignments used for leaf and spine

switches in the BGP examples in this guide.

Rack 2Rack 1

64601 64602

VLT i

64702

64701

64703

64704

BGP ASN assignments

ASNs should follow a logical pattern for ease of administration and allow for growth as additional leaf and

spine switches are added. In this example, an ASN with a "6" in the hundreds place represents a spine switch

(e.g. 64601) and an ASN with a "7" in the hundreds place represents a leaf switch (e.g. 64701).

6.2 IP addressing

Establishing a logical, scalable IP address scheme is important before deploying a leaf-spine topology. This

section covers the IP addressing used in the layer 3 examples in this guide.

6.2.1 Loopback addresses

Loopback addresses may be used as router IDs when configuring routing protocols. As with ASNs, loopback

addresses should follow a logical pattern that will make it easier for administrators to manage the network and

allow for growth. Figure 12 shows the loopback addresses used as router IDs in the BGP and OSPF

examples in this guide.