NetOps Toolkit

Cisco IOS

BGP/EIGRP Commands

Interactive BGP and EIGRP config generators with show commands and troubleshooting

BGP vs EIGRP — When to Use Which

Border Gateway Protocol (BGP) is a path-vector routing protocol used primarily between autonomous systems (Internet, ISP, WAN edge) and for large-scale policy-based routing.

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector protocol used inside an organization for fast convergence and simple operation.

Key Characteristics

Feature BGP EIGRP
Type Path-vector (policy based) Advanced distance-vector (hybrid)
Typical Use Internet, WAN edge, multi-homing, DC fabrics Campus / enterprise interior routing
Metric Path attributes (AS-path, local-pref, MED, communities) Composite metric: bandwidth, delay, reliability, load, MTU
Transport TCP port 179 IP protocol 88 (no TCP/UDP port)
Neighbor Discovery Manual neighbor configuration Multicast hello (224.0.0.10) and manual neighbors on NBMA
Scalability Very high, millions of prefixes with policies High inside an AS, not Internet-scale
Use BGP where you need policy and Internet reachability; use EIGRP inside the enterprise where fast convergence and simpler configs matter.

BGP Essentials

  • Forms explicit neighbor relationships over TCP 179.
  • Exchanges full routing tables, then incremental updates.
  • Best-path selection uses local-pref, AS-path length, origin, MED, eBGP vs iBGP, IGP metric, router ID.
  • iBGP requires full-mesh, route reflectors, or confederations for scale.
  • Commonly used to advertise default routes and specific prefixes to customers/peers.

EIGRP Essentials

  • Uses Diffusing Update Algorithm (DUAL) for loop-free fast convergence.
  • Supports unequal-cost load balancing with the variance command.
  • Uses hello/hold timers and feasible successors for backups.
  • Can summarize routes at any interface to keep the topology small.
  • Supports IPv4 and IPv6 with classic and named mode configurations.

Design Tips

BGP at Edge
Terminate ISP links and control outbound/inbound traffic with local-pref, MED, communities.
EIGRP in Core
Use EIGRP for internal routing, summarizing at distribution to keep core tables small.
Redistribution
Carefully plan BGP<->EIGRP redistribution to avoid loops; tag and filter routes.
Warning: Mixing many protocols and uncontrolled redistribution can create loops and suboptimal paths. Keep the design simple.