Blog Posts in April 2014

Declarative and Procedural Programming (and How I Got It all Wrong)

During a recent NetOps-focused discussion trying to figure out where Puppet/Chef/Ansible/… make sense in the brave new SDN-focused networking world I made this analogy: “Puppet manifest is like Prolog, router configuration is like Java or C++.” It’s a nice sound bite. It’s also totally wrong.

If you never met Prolog, you might consider yourself lucky. Or you might want to figure out what it is (warning: it might make your head explode). Just joking, I actually quite liked it in my programming days.
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Security in Leaf-and-Spine Fabrics

One of my readers sent me an interesting question:

How does one impose a security policy on servers connected via a Clos fabric? The traditional model of segregating servers into vlans/zones and enforcing policy with a security device doesn’t fit here. Can VRF-lite be used on the mesh to accomplish segregation?

Good news: the security aspects of leaf-and-spine fabrics are no different from more traditional architectures.

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Why Exactly Would You Want a Nexus 7000 in There?

Network designers (and smart consulting and system integration companies) often use ExpertExpress to get a second opinion on a design someone put together using technologies they’re not thoroughly familiar with. Not surprisingly, some of those third-party designs aren’t exactly optimal.

A while ago I was asked to review a data center “design” proposed to my customer by a system integrator. It had a pair of Nexus 5500 switches connecting servers and storage to a single Nexus 7000, which was then connected to WAN edge routers.

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Brocade Shipped VXLAN VTEP with NSX Controller Support

Update 2021-01-03: NSX-V is enjoying its retirement, making any related VXLAN hardware gateways obsolete. In the meantime, VMware NSBU came to their senses and implemented EVPN in NSX-T 3.0, VCS Fabric is long gone, and Ethernet part of Brocade was acquired by Extreme.

Brook Reams sent me an interesting tidbit: Brocade is the first vendor that actually shipped a VXLAN VTEP controlled by a VMware NSX controller. It’s amazing to see how Brocade leapfrogged everyone else (they also added tons of other new functionality in NOS releases 4.0 and 4.1).

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Distributed DoS Mitigation with OpenFlow

Distributed DoS mitigation is another one of the “we were doing SDN without knowing it” cases: remote-triggered black holes are used by most major ISPs, and BGP Flowspec was available for years. Not surprisingly, people started using OpenFlow to implement the same concept (there’s even a proposal to integrate OpenFlow support into Bro IDS).

For more details, watch the Distributed DoS Prevention video recorded during the Real Life OpenFlow-based SDN Use Cases webinar.

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Puppet Is a Tool, DevOps Is a Lifestyle

During Interop 2014 I got involved in numerous interesting conversations revolving around SDN and new operations models (including the heretic idea of bundling appliances with application stacks and making developers responsible for network services).

During one of those discussions someone said “I think I get the ideas behind DevOps, but I don’t think we should configure our network devices with Puppet or Chef” to which I replied “Puppet or Chef are just tools, DevOps is a lifestyle.

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Troubleshooting Residential IPv6 Connectivity

Most ISPs rolling out large-scale residential IPv6 (bringing US to ~7%, Switzerland to ~10% and Belgium above 16%) agree it’s a no-brainer, but the rest of the world still hesitates.

To help the dubious majority cross the (perceived) shaky bridge across the gaping chasm between IPv4 and IPv6, a team of great engineers with decades of IPv6 operational experience (including networking gurus from Time Warner, Comcast and Yahoo, and the never-tiring IPv6 evangelist Jan Žorž) wrote an IPv6 Troubleshooting for Helpdesks document.

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Network Function Virtualization (NFV) 101

When I first heard about NFV, I thought it was just another steaming pile of hype designed to push the appliance vendors to offer their solutions in VM format. After all, we’re past the hard technical challenges: most appliances deserve to have an Intel Inside sticker, performance problems have been addressed (see Intel DPDK, 6WIND, PF_ring and Snabb Switch), so what’s stopping us from deploying NFV apart from stubborn vendors who want to sell hardware, not licenses?

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Changes in IBGP Next Hop Processing Drastically Improve BGP-based DMVPN Designs

I always recommended EBGP-based designs for DMVPN networks due to the significant complexity of running IBGP without an underlying IGP. The neighbor next-hop-self all feature introduced in recent Cisco IOS releases has totally changed my perspective – it makes IBGP-over-DMVPN the best design option unless you want to use DMVPN network as a backup for MPLS/VPN network.

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Three Common Mistakes That Can Doom Your Private Cloud

In the first half hour of the Infrastructure for Private Clouds workshop at last week’s Interop Las Vegas I focused on business aspects of private cloud design: defining the customers, the services, and the level of self-service you’ll offer to your customers.

Nick Martin published a great summary of these topics @ SearchServerVirtualization; I couldn’t have done it better myself (they want to get your email address, but this article is definitely worth it).

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Should We Use Redundant Supervisors?

I had a nice chat with Doug Gourlay from Arista during the Interop Las Vegas and he made an interesting remark along the lines of “in leaf-and-spine fabrics it doesn’t make sense to use redundant supervisors in switches – they cause more problems than they solve.”

As always, in the end it all depends on your environment and use case, but he definitely has a point; good engineering always works better than a heap of kludges.

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Real Life BGP Route Origination and BGP Next Hop Intricacies

During one of the ExpertExpress engagements I helped a company implement the BGP Everywhere concept, significantly simplifying their routing by replacing unstable route redistribution between BGP and IGP with a single BGP domain running across MPLS/VPN and DMVPN networks.

They had a pretty simple core site network, so we decided to establish an IBGP session between DMVPH hub router and MPLS/VPN CE router (managed by the SP).

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Quantum SDN

An interesting startup is launching their SDN solution @ Interop Las Vegas today: Quantum Networks use the latest quantum computing technology to solve some of the hardest problems of controller-based networking.

One of the fundamental problems of hardware-based OpenFlow solutions is the flow update rate – most switches using merchant silicon can insert around 1000 new flows per second into their forwarding tables. Technologies based on quantum mechanics effects change all that – a quantum entanglement technology patented by Quantum Networks can install new flows instantaneously across the whole network.

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