[j-nsp] EX4600 or QFX5110

Anderson, Charles R cra at wpi.edu
Tue Mar 12 14:56:40 EDT 2019

Spanning Tree is rather frowned upon for new designs (for good reasons).  Usually, if you have the ability to do stright L2 bridging, you can always do L3 on top of that.  A routed Spine/Leaf design with EVPN-VXLAN overly for L2 extension might be a good candidate and is typically the answer given these days.

I'm not a fan of proprietary fabric designs like VCF or MC-LAG.  VC is okay, but I wouldn't use it across your entire set of racks because you are creating a single management/control plane as a single point of failure with shared fate for the entire 6 racks.  If you must avoid L3 for some reason, I would create a L2 distribution layer VC out of a couple QFX5110s and dual-home independent Top Of Rack switches to that VC so each rack switch is separate.  I've used 2-member VCs with QFX5100 without issue.  Just be sure to enable "no-split-detection" if and only if you have exactly 2 members.  Then interconnect the distribution VCs at each site with regular LAGs.

On Tue, Mar 12, 2019 at 06:36:49PM +0000, Alex Martino via juniper-nsp wrote:
> Hi,
> I am seeking advices.
> I am working on a L2/L3 DC setup. I have six racks spread across two locations. I need about 20 ports of 10 Gbps (*2 for redundancy) ports per rack and a low bandwidth between the two locations c.a. 1 Gbps. Nothing special here.
> At first sight, the EX4600 seems like a perfect fit with Virtual Chassis feature in each rack to avoid spanning tree across all racks. Essentially, I would imagine one VC cluster of 6 switches per location and running spanning-tree for the two remote locations, where L3 is not possible.
> I have been told to check the QFX5110 without much context, other than not do VC but only VCF with QFXs. As such and after doing my searches, my findings would suggest that the EX4600 is a good candidate for VC but does not support VCF, where the QFX5110 would be a good candidate for VCF but not for VC (although the feature seems to be supported). And I have been told to either use VC or VCF rather than MC-LAG.
> Any suggestions?
> Thanks,
> Alex

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