Month: January 2018

Datacenter Design II (Blades, Scaling, Bandwidth)

Blade Server design

  • Overleg with the server team connectivity.
  • Many blade servers enter de “enterprise switch” market with an integrated switch.
  • Pass-through cabling or integrated switches.
  • Significant impact on power – cooling – weight.

Connecting the blade to the network

  • If you use the integrated blade switch, use a layer3 access layer.
  • Avoid a double Layer 2 design:
    •  [Layer 2 on the access layer] connected to a [layer 2 domain within the bladeswitch].
  • If you use passthrough, use a layer2 or layer3 access layer.

Scaling the Datacenter Architecture


Datacenter Design I (Core, Aggregation, Access Designs)


  • Not all datacenter designs needs a core layer
  • Access to aggregation, aggregation to core : 10 or 40GBps
  • CEF load balancing tuning (L3 + L4)
  • Core should run L3 only, Aggregation acts as L3/L2 boundry to access
  • Core runs OSPF / EIGRP with aggregation



Wan Services (Sonet, Metro, VPLS, MPLS)


Sonet ( Synchronous Optical Networking)

  • American National Standards Institute (ANSI)
  • Used in US / Canada
  • Synchronous transport signals (STS) used for speed

Synchronous Digital Hierarchy

  • International Telecommunications union (ITU)
  • Used everywhere expect US / Canada
  • Synchronoous transport Modules (STM) used for speed)


IP Subnetting Template

10.1.40.Y40Servers Printers
10.1.50.y50Exit VLAN
10.1.98.Y98Public WiFI
10.2.40.Y40Servers Printers
10.2.50.y50Exit VLAN
10.2.98.Y98Public WiFI



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! )