Switch – Top of Rack Switching, No Single Point of Failure


Assume that you have 1 rack in a reliable colo facility. The colo (obviously) has advanced chassis switches and can provide any reasonable manner of drops specified (but a limited number of drops). That is to say, you can specify two GB cat6 drops configured such that (specify additional config here).

Also assume that you have N (say 10) "servers" each with 2 GB ethernet ports. Each server needs to have one always accessible, routable ip address. That is to say, each server has an IP address WWW.XXX.YYY.ZZZ that should be pingable from any properly configured host on the internet.

What is the simplest logical and phsical network topology you can install top of rack such that there is no one single point of failure leading to ip connectivity issues between the servers and the gateway provided by the colo?

By simple, I mean, generally speaking, cheapest to implement using Cisco networking gear. That is a rough definition, but I think it should correlate well with the answer I am after.

Best Answer

A couple of refinements to Rune's suggestion:

  • if you use Cisco Catalyst 3750's, the stacking cable will eliminate spanning-tree between the switches, provide greater bandwidth and redundancy without using host ports.
  • If the colo has Cisco 6500 core's with the sup720 VSS blades, then you can do Etherchannel on the 3750's to virtual-Etherchannel on the cores (switch1 -> core1 & switch2 -> core2) further reducing spanning-tree
  • If supported by the colo:
    • use HSRP, VRRP or GLBP for gateway redundancy
    • implement UDLD aggressive on the uplinks (assuming they are fiber)
  • consider using RPS units for power redundancy on the 3750's
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