netlab 1.6.2: More Reporting Goodies

netlab release 1.6.2 improved reporting capabilities:

  • BGP reports and IP addressing reports are fully IPv6-aware
  • Some columns in BGP reports are optional to reduce the width of text reports
  • You can filter the reports you’re interested in when using netlab show reports command
  • Reports relying on ipaddr Ansible filter display warnings (instead of crashing) if you don’t have Ansible installed.

In other news:

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How GitHub Saved My Day

I always tell networking engineers who aspire to be more than VLAN-munging CLI jockeys to get fluent with Git. I should also be telling them that while doing local version control is the right thing to do, you should always have backups (in this case, a remote repository).

I’m eating my own dog food1 – I’m using a half dozen Git repositories in ipSpace.net production2. If they break, my blog stops working, and I cannot publish new documents3.

Now for a fun fact: Git is not transactionally consistent.

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Why Do We Need Source IP Addresses in IP Headers?

After discussing names, addresses and routes, and the various addresses we might need in a networking stack, we’re ready to tackle an interesting comment made by a Twitter user as a reply to my Why Is Source Address Validation Still a Problem? blog post:

Maybe the question we should be asking is why there is a source address in the packet header at all.

Most consumers of network services expect a two-way communication – you send some stuff to another node providing an interesting service, and you usually expect to get some stuff back. So far so good. Now for the fun part: how does the server know where to send the stuff back to? There are two possible answers1:

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Does EVPN/VXLAN over SD-WAN Make Sense?

It looks like we might be seeing VXLAN-over-SDWAN deployments in the wild. Here’s the “why that makes sense” argument I received from a participant of the ipSpace.net Design Clinic in which I wasn’t exactly enthusiastic about the idea.

Also, the EVPN-over-WAN idea is not hypothetical since EVPN+VXLAN is now the easiest way to build L3VPN with data center switches that don’t support MPLS LDP. Folks with no interest in EVPN’s L2 features are still using it for L3VPN.

Let’s unravel this scenario a bit:

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Addresses in a Networking Stack

After discussing names, addresses and routes, it’s time for the next question: what kinds of addresses do we need to make things work?

End-users (clients) are usually interested in a single thing: they want to reach the service they want to use. They don’t care about nodes, links, or anything else.

End-users might want to use friendly service names, but we already know we need addresses to make things work. We need application level service identifiers – something that identifies the services that the clients want to reach.

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Names, Addresses, and Routes

It always helps to figure out the challenges of a problem you’re planning to solve, and to have a well-defined terminology. This blog post will mention a few challenges we might encounter while addressing various layers of the networking stack, from data-link layer and all the way up to the application layer, and introduce the concepts of names, addresses and routes.

According to Martin Fowler, one of the best quotes I found on the topic originally came from Phil Karlton:

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Dataplane MAC Learning with EVPN

Johannes Resch submitted the following comment to the Is Dynamic MAC Learning Better Than EVPN? blog post:

I’ve also recently noticed some vendors claiming that dataplane MAC learning is so much better because it reduces the number of BGP updates in large scale SP EVPN deployments. Apparently, some of them are working on IETF drafts to bring dataplane MAC learning “back” to EVPN. Not sure if this is really a relevant point - we know that BGP scales nicely, and its relatively easy to deploy virtualized RR with sufficient VPU resources.

While he’s absolutely correct that BGP scales nicely, the questions to ask is “what is the optimal way to deliver a Carrier Ethernet service?

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