It seems building a network is full of disaster, there are choices to be made more sticky than plaster. Most protocols talk but the new ones do not, and we don't want to be stuck with EIGRP rott. They are complex and closed like a private race track, We thought STP was dead, but it's TRILL that is back. My advice to my friends is to chose what is chosen, use lots of good drafts from Kompella and Rosen. Be afraid of the vendors that meddle and try, to make you chose products that will wither and die, but chose with your money, your money and buy. Buy open systems, with drafts you can read, do-it-yourself or hire PS if you need. And script it all up, and make sense of the mess, use NETCONF or YANG or some other fine REST. Blackboxes may work, but the understanding they lack, it's a terrible choice for a new top-of-rack, your servers must send, through pipes that do bend, and when black boxes stop, it's protocols that must mend, to advertise vectors, and places of reach, and this is why I stand on my soapbox and preach. When building a fabric, one must have to think, it's a slippery slope like a ice hockey rink. Do I want a good product or build it yourself? QFabric or Cisco have a method that's theirs, and TRILL or OpenFLow have me jumping from chairs. Make sure that the choice has no method to trap, from signaling, datapath, and even encap. A packet's a packet, but with multicast it grows, make sure that your mroute state copes with the flows, and that over your tunnels you can compose, efficiency is realised when transport is exposed. No ships in the night, it must work over and under, your building a network that's full of wonder. No crashing above like a sky full of thunder. Before you CONF T, and before you ENABLE, make sure that you sorted out your Ethernet cable, is it fibre and optics, or copper and DAC, one's cheaper than the other, the others a pain in the rack. Do you put a big box at the end of the row? Or you looking to scale, are you looking to grow? If that is the case, at the top it must be, but are you comfortable with a LEAF SPINEY TREE? Is it lots of gigabits do you need 40GE? Have no fear how you build it, In you I do trust, you will scale it and scale it, and scale it you must! Your links will come up, your lights will blink to the brightest, They will blink on the leftest, they will blink on the rightest! All your packets will forward, your TTL's will change, and most of the time the errors will range, your links will stay up, your WAN will as well, it's because you hooked your syslog to a bell! In 10 years from now when we are all IPv6, we will be proud of your challenge, your challenge and risk! You could have just listened to your vendor with vigor, but you built a fantastic, vertical and horizontal figure; you linked up the east, and you linked up the west, and for that your HADOOP HDFS is the best. You hooked up the north, for your traffic to enter, We took all the data and put it in the center.