Routing Design Principles (EIGRP, OSPF, BGP)

EIGRP design principles

  • EIGRP works for arbitrary topologies for small to medium networks.
  • A flat EIGRP network doesn’t really scale beyond 400 routers and will lead to performance issuse
    • How to solve this?
      • Stub areas, summerization, route filtering limits the query scope
  • If EIGRP doesn’t have a feasible successor it will query all it’s neighbours.
    • “I don’t have a route anymore, don’t route through me, give me a viable route”.
  • BFD to optimize convergence (100ms wtih 1000 routes).
  • 2 second hello timer, 6 second hold timer ( recommended )

Multiple EIGRP design principles

  • Used to merge two networks ( Acquisitions )
  • Different administrative groups in a company
  • a way to devide large networks ( and control queries )
  • Routes are distributed between AS ( don’t loop! )

OSPF design principles

  • Number of neighbouring routers ( no more than 60 ).
  • Number of routers in an area ( no more than 50 ).
  • Number of areas connected to a router ( no more than 3 ).
    • LSDB has to be maintained for all area’s
  • The router acting as the DR ( best router).
  • Ammount of data in an area impatcs OPSF performance
    • Summarize
    • Stub / Total stub
  • Areas should be designed around geography and functional boundries
  • Summarization minimizes route change (flapping) impact
  • Large networks only have ARBS in AREA 0
  • Contigious splitable adressing

BGP design principles

  • BGP as IGP:
    • Advantages: 
      • Vendor interoperability
      • per-hop traffic engineering,
      • unequal-cost loadbalancing / anycast routing
      • simpler troubleshouting (as-path)
      • reduced flooding
      • Trust border controll
    • Disadvantages:
      • Default timers are very slow
      • Not available on low-end routers (layer 3 switches)
      • Not as dynamic
      • Full mesh requirement
  • Route Reflector design
  • Confederate design

All Routing protocols

All routing protocols must detect, propagate, process and update.

Add a Comment

Your email address will not be published. Required fields are marked *

Reload Image