Deployment Guide

9 Dell EMC Networking Layer 3 Leaf-Spine Deployment and Best Practices with OS10 | Version 1.0
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4 Protocols used in the leaf-spine examples
This section provides an overview of the protocols used in constructing the leaf-spine network examples in
this guide.
 VLT, Section 4.1
 LACP/LAG, Section 4.2
 Uplink Failure Detection (UFD), Section 4.3
 RSTP, Section 4.4
 Routing protocols, Section 4.5
- Border Gateway Protocol (BGP)
- Open Shortest Path First (OSPF)
 VRRP, Section 4.6
 ECMP, Section 4.7
4.1 Virtual Link Trunking (VLT)
VLT allows link aggregation group (LAG) terminations on two separate switches and supports a loop-free
topology. The two switches are referred to as VLT peers and are kept synchronized via an inter-switch link
(ISL) called the VLT interconnect (VLTi). A separate backup link maintains heartbeat messages across the
OOB management network or using a point-to-point link between peers.
VLT provides layer 2 multipathing and load-balances traffic. VLT offers the following additional benefits:
 Eliminates spanning tree-blocked ports
 Uses all available uplink bandwidth
 Enables fast path switchover if either a link or device fails
 Ensures high availability
Note: Downstream connections from leaf switches configured for VLT do not necessarily have to be
configured as LAGs if other fault tolerant methods are preferred (e.g. multipath IO). In this guide, examples 1
and 2 use LAGs to downstream servers while examples 3 and 4 do not.
4.2 LACP/LAG
Link Aggregation Group (LAG) bundles multiple links into a single interface to increase bandwidth between
two devices. LAGs also provide redundancy via the multiple paths. In a leaf-spine network, LAGs are typically
used to attach servers or storage devices to the VLT leaf pairs.
Link Aggregation Control Protocol (LACP) is an improvement over static LAGs in that the protocol will
automatically failover if there is a connectivity issue. This is especially important if the links traverse a media
converter where it is possible to lose Ethernet connectivity while links remain in an Up state.