I love my Juniper switches. I've been using Cisco for years, but the Junos system just rocks. Add to that, their Virtual Chassis system, and I've been very pleased on the results. I wanted to put together a quick post on how I use the 4200's in a server environment. See the image for reference:
Basically, because each switch is connected via "Virtual Chassis", they operate as a single switch. So, for each of my VMWare hosts, or physical servers, I build a link aggregation (some call it teaming, etherchannel, or 802.3ad) to different switches. Because they act as a single switch, I get the full bandwidth and speeds of the aggregate. However, if one switch were to fail, I still have failover as the aggregate will be down to n-1.
Also, in the back, you can see how I "chain" my switches for redundancy. Each link carries up to 64Gbps of "fabric" traffic. If one link fails, the switches will redirect those frames through another link. For those that LOVE marketing babble, yes, that means 128Gbps total, since you have two links to each switch.
Since I've implemented the 4200's, I couldn't be happier. Plus, upgrading will be a cinch, since the Juniper 4500's (their 10Gbps switches) can also participate in the same Virtual Chassis. So, upgrading to 10Gb is as simple as adding another switch.
Finally, my last point. I hear in discussions all the time, that "....if you use Virtual Chassis, you do not need STP." This bothers me. We should not be using that term so loosely. Yes, the links *between* the switches (the Virtual Chassis Links) do not need STP. So, that statement is correct. However, it *almost* implies that STP does not need to be enabled at all.
Enable STP! While your Virtual Chassis may be safe, who's to say that another switch can't be connected to it?