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Management Subnet... To route or not to route...


So, I am going through the process of laying out management IP address's for a Datacenter and was wondering if I could get some or your opinions... After reading on the topic,

I have seen 2 different schools of thought...

A management VLAN that is trunked to all switches in the datacenter... This approach is simple, yet , I see some weakness therein:

  • Single broadcast domain (unless you implement multiple Management VLAN's and subnets)
  • All devices rely on the same device(s) for there default GW & associated routing functions
  • etc...

So, the other approach is to use management VLAN's on L2 devices and use Loopback's on L3 devices... This solution addresses some of the weaknesses above, yet add's some complexity:

  • Requires the involvement of (a) routing protocol\static routes
  • Routed interfaces upstream to form IGP adjacencies over, thus disallowing L2 to extend from one Top of Rack switch to another
    • OR
  • Selecting a transit VLAN, assigning a /31 range to neighbors and routing over that VLAN
    • This approach is nice in that it maintains the ability for VLAN trunking to\through L3 switches
  • Full routing tables on these devices where, for the most part, they and downstream devices will be more L2 focused
    • One could, using Stub routing, eliminate the full routing table overhead, but that actually adds to the overhead:
      • If OSPF was the IGP, then you would need to create a "management" area for loopback managed device's to allow you to implement Totally stubby area benefits...
  • Etc...

So, what are your thoughts? Which approach do you all use\prefer?


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