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



  • Datacenter Core as NSSA.
    • Campus core wille be your backbone area (area 0).
  • Summerize Routes to Campus.
  • Default Route from campus.
  • Authentication / tuning.


  • Summery-addressto advertize campus default.
  • Summery-address to sum up datacenter.
  • Authentication / tuning.

Service modules

  • Using Cisco Modular switches for service modules:
    • Content switching (CSM) / Application Control Engine ( ACE )
    • Firewall Service Module ( FWSM )
    • Intrustion Prevention ( IPS )
    • Wireless ( WISM )


Looped designs, redundant linked blocked by STP.
All links in the layer2 domain.

Designs without STP implementation ( Faster convergence):

Flexlink design ( Disables STP with Active/Passive links).

Layer 3 access layer design:

  • Each pair of switches are a L2 domain.
  • Access layer uplinks are load balanced.
  • STP still runs on the access layer.
  • IP address space takes more management.
  • Difficult migration.
  • Service Modules needed within access layer switches.


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