Enhanced Interior Gateway Routing Protocol (EIGRP)

EIGRP was the best choice for an interior gateway protocol in late 1990s – it was fast, efficient, and easy to deploy. OSPF and IS-IS implementations improved in the intervening 30 years, slowly turning EIGRP into a forgotten technology.

On a more serious note, I wouldn’t deploy EIGRP in new network designs for compatibility reasons (no major networking vendor apart from Cisco implemented it), and I’d use BGP in designs where a single router has to deal with hundreds of adjacent routers (the only scenario where EIGRP still outshines OSPF and IS-IS).

While the ultimate sources of EIGRP wisdom remain the EIGRP Network Design Solutions Cisco Press book and RFC 7868, you might want to read these articles and blog posts describing EIGRP implementation details and deployment guidelines.

The Basics

• Scaling EIGRP Networks with Stub Routers
• EIGRP Myths Debunked
• EIGRP: an MBA-Like Perspective
• EIGRP Loop Prevention Logic
• RFC 7868: The Definitive EIGRP Guide
• Missing Information for the EIGRP Network Design Solutions Cisco Press Book

Implementation Details

• EIGRP Goodbye Message
• EIGRP Load Balancing Based on Interface Load
• Changes in EIGRP Summary Address Are no Longer Disruptive
• EIGRP Neighbor Loss Detection
• EIGRP Load and Reliability Metrics
• EIGRP MTU “metric”
• EIGRP Offset Lists
• Beware of the Pre-Bestpath Cost Extended BGP Community
• EIGRP Third-Party Next Hops

EIGRP Deployment Scenarios

• Using EIGRP in MPLS VPN Networks
• Multihomed EIGRP Sites in MPLS VPN Network
• Leak Map Confusion
• Limitations of VRF Routing Protocols on Cisco IOS
• GRE Keepalives or EIGRP Hellos?
• Recommendations for Keepalive/Hello Timers
• Manipulating EIGRP Metrics
• Multiple EIGRP Autonomous Systems in a VRF
• EIGRP Summarization in DMVPN Phase 2 Networks
• Solution: EIGRP Summarization Breaks Phase 2 DMVPN
• OSPF Meets EIGRP
• IBGP, IGP Metrics, and Administrative Distances
• Does Unequal-Cost Multipathing Make Sense?