Deployment Guide
Table Of Contents
- 1 Introduction
- 2 Hardware overview
- 3 Leaf-spine overview
- 4 Protocols used in the leaf-spine examples
- 5 Layer 3 configuration planning
- 6 Example 1: Layer 3 with Dell EMC leaf and spine switches using OSPF
- 7 Example 2: Layer 3 with Dell EMC leaf and spine switches using eBGP
- A Dell EMC Networking ONIE switch factory default settings
- B Validated hardware and operating systems
- C Technical support and resources
- D Support and Feedback
11 Dell EMC Networking Layer 3 Leaf-Spine Deployment and Best Practices with OS10 | Version 1.0
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of switch misconfiguration or improperly connected cables. In properly configured and connected leaf-spine
networks, there are no ports blocked by Spanning Tree Protocol.
4.5 Routing protocols
Any of the following routing protocols may be used on layer 3 connections when designing a leaf-spine
network:
OSPF
BGP
4.5.1 Border Gateway Protocol (BGP)
BGP may be selected for scalability and is well suited for very large networks. BGP can be configured as
External BGP (eBGP) to route between autonomous systems or Internal BGP (iBGP) to route within a single
autonomous system.
Layer 3 leaf-spine networks use ECMP routing. eBGP and iBGP handle ECMP differently. By default, eBGP
supports ECMP without any adjustments. To keep configuration complexity to a minimum, Dell EMC
recommends eBGP in leaf-spine fabric deployments.
BGP tracks IP reachability to the peer remote address and the peer local address. Whenever either address
becomes unreachable, BGP brings down the session with the peer. To ensure fast convergence with BGP,
Dell EMC recommends enabling Neighbor fall-over with BGP. Neighbor fall-over terminates BGP sessions of
any directly adjacent peer if the link to reach the peer goes down without waiting for the hold-down timer to
expire.
4.5.2 Open Shortest Path First (OSPF)
OSPF is an interior gateway protocol that provides routing inside an autonomous network. OSPF routers send
link-state advertisements to all other routers within the same autonomous system areas. While generally more
memory and CPU intensive than BGP, OSPF may offer faster convergence. OSPF is often used in smaller
networks (100 OSPF routers, depending on various factors).
4.6 Virtual Router Redundancy Protocol (VRRP)
VRRP is a first hop redundancy protocol. It provides gateway redundancy by enabling a pair of VRRP routers
to coordinate and act as one gateway. This way, if one VRRP router fails, the other router will detect its
missing peer, and become the active gateway.
Although VRRP is traditionally an active/standby protocol, wherein only one VRRP router does the forwarding
at a time, when used between VLT peers, it becomes active/active. Even the backup VRRP router will forward
packets for hosts and end devices.
In this guide, VRRP version 3 is specified. VRRP version 3 supports IPv6. VRRP version 3 requires higher
priority for preemption (with version 2, if both routers have the same priority, the router with the higher IP
address will preempt). Version 3 also uses millisecond timers for improved tunability.