Using a BGP Route Server in an Internet Exchange Point

A BGP route server is like a BGP route reflector but for EBGP sessions. In its simplest implementation, it receives BGP updates over EBGP sessions and propagates them over other EBGP sessions without inserting its own AS number in the AS path (more details).

BGP route servers are commonly used on Internet Exchange Points (IXPs), and that’s what you can practice in the BGP Route Server in an Internet Exchange Point lab exercise.

Click here to start the lab in your browser using GitHub Codespaces (or set up your own lab infrastructure). After starting the lab environment, change the directory to session/5-routeserver and execute netlab up.

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netlab 1.9.2: STP, LAG, Cisco IOL, Edgeshark

While I was busy fixing bugs in the netlab release 1.9.2, other contributors added exciting new features:

Other new features include:

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EVPN Designs: EVPN EBGP over IPv4 EBGP

In the previous blog posts, we explored three fundamental EVPN designs: we don’t need EVPN, IBGP EVPN AF over IGP-advertised loopbacks (the way EVPN was designed to be used) and EBGP-only EVPN (running the EVPN AF in parallel with the IPv4 AF).

Now we’re entering Wonderland: the somewhat unusual1 things vendors do to make their existing stuff work while also pretending to look cool2. We’ll start with EBGP-over-EBGP, and to understand why someone would want to do something like that, we have to go back to the basics.

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netlab: How do I Specify VLAN Interface Parameters

Similarly to how it handles VRFs, netlab automatically creates VLANs on a lab device if the device uses them on any access- or trunk link or if the VLAN is mentioned in the node vlans dictionary.

If the VLAN is an IRB VLAN (which can be modified globally or per node with the VLAN mode parameter), netlab also creates the VLAN (or SVI, or BVI) interface. But how do you specify the parameters of the VLAN interface?

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Per-Prefix and Per-VRF MPLS/VPN and EVPN Labels/VNIs

Long long time ago1, in an ancient town far far away2, an old-school networking Jeddi3 was driving us toward a convent4 where we had an SDN workshop5. While we were stuck in the morning traffic jam, an enthusiastic engineer sitting beside me wanted to know my opinion about per-prefix and per-VRF MPLS/VPN label allocation.

At that time, I had lived in a comfortable Cisco IOS bubble for way too long, so my answer was along the lines of “Say what???” Nicola Modena6 quickly expanded my horizons, and I said, “Gee, I have to write a blog post about that!” As you can see, it took me over a decade.

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Lab: Configure IS-IS on Point-to-Point Links

From a very high-level perspective, OSPF and IS-IS are quite similar. Both were created in the Stone Age of networking, and both differentiate between multi-access LAN segments and point-to-point serial interfaces. Unfortunately, that approach no longer works in the Ethernet Everywhere world where most of the point-to-point links look like LAN segments, so we always have to change the default settings to make an IGP work better.

That’s what you’ll do in today’s lab exercise, which also explains the behind-the-scenes differences between point-to-point and multi-access links and the intricate world of three-way handshake.

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NOG.HR: A NOG Meeting Worth Attending

I never know what to expect when I’m invited to speak at a regional (or in-country) Network Operator Group (NOG) meeting. Sometimes, it turns out to be a large conference (PLNOG and ITNOG come to mind); other times, it’s just a few people gathered around free donuts and coffee1. Last week’s Croatian NOG (NOG.HR) meeting was in the Goldilocks zone between the extremes: plenty of interested networking engineers, but not large enough to be overpowering.

Also, it was such a nice experience ;)

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Comparing IP and CLNP: Finding Adjacent Nodes

Now that we know a bit more about addresses in a networking stack (read the whole series) and why CLNP uses node addresses while TCP/IP uses interface addresses, let’s see how they solve common addressing problems like finding adjacent nodes.

Let’s start with the elephant in the room: how do you know whether you can reach a host you want to communicate with directly? In the following diagram, how does A know whether B is sitting next to it?

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