Having “do we need ULA” blogologs with Ed Horley is great … and the best part of them is that we’re both right (aka: It Depends). OK, let’s try to quantify that last part.

Almost three years ago the OpenFlow/SDN hype exploded and the Open Networking Foundation started promoting the concept of physically separate control and data planes. Let’s see how far its founding members got in the meantime:

Chris Wahl claimed in one of his recent blog posts that vSphere doesn't need LAG band-aids. He's absolutely right – vSphere’s loop prevention logic alleviates the need for STP-blocked links, allowing you to use full server uplink bandwidth without the complexity of link aggregation. Now let’s consider the networking perspective.

More news from the IPv6 is not like IPv4 department: there's no DF bit in IPv6, so you have to use slightly different troubleshooting tricks to figure out the path MTU size (and they depend on the operating system). More in a detailed blog post by my good friend Matjaž Straus.

The first part of the Real-life OpenFlow Use Cases webinar focused on controller design and implementation choices that can significantly impact the scalability of an OpenFlow solution:

• Proactive versus reactive flow setup;
• Hop-by-hop versus path-based forwarding;
• State explosion with OpenFlow 1.0;

You could tell we had great fun with these topics: we spent more than half an hour on five slides.

When Open Networking Foundation claimed ownership of Software-Defined Networking, they defined it as separation of control and data plane:

[SDN is] The physical separation of the network control plane from the forwarding plane, and where a control plane controls several devices.

Does this definition make sense or is it too limiting? Is there more to SDN? Would a broader scope make more sense?

During my ExpertExpress engagements with engineers building multi-tenant cloud infrastructure I often get questions along the lines of “How do I integrate my public IaaS cloud with my MPLS/VPN WAN?” Here are a few ideas.

My recommendation to use ULA addresses for internal communications within organizations that don’t have their own provider-independent address space resulted in the following comment:

[…] Having ULA for internal company communication and global IPv6 addresses for communication with the Internet will cause lots of issues with application guys since now application has to bind to specific IPv6 address for internal communications and another IPv6 address to go to the Internet.

Numerous aspects of IPv6 may still be broken, but fortunately this is not one of them.

Software-Defined Networking is clearly a tautological term – after all, software defined networking device behavior ever since we stopped using Token Ring MAUs and unmanaged hubs. Open Networking Foundation claims it owns the definition of the term (which makes approximately as much sense as someone claiming they own the definition of red-colored clouds), but I was always wondering who coined the term in the first place.

Gordon sent me a whole list of NSX gateway questions:

• Do you need a virtual gateway for each VXLAN segment or can a gateway be the entry/exit point across multiple VXLAN segments?
• Can you setup multiple gateways and specify which VXLAN segments use each gateway?
• Can you cluster gateways together (Active/Active) or do you setup them up as Active/Standby?

The answers obviously depend on whether you’re deploying NSX for multiple hypervisors or NSX for vSphere. Let’s start with the former.