One of my friends is running a large IPv6 network and has already experienced a shortage of IPv6 neighbor cache on some of his switches. Digging deeper into the root causes, he discovered:

In my larger environments, I see significant neighbor table cache entries, especially on network segments with hosts that make many long-term connections. These hosts have 10 to 20 addresses that maintain state over days or weeks to accomplish their processes.

What’s going on? A perfect storm of numerous unrelated annoyances:

Lasse Haugen had enough of the never-ending “we can’t possibly deploy IPv6” excuses and decided to start the IPv6 Shame-as-a-Service website, documenting top websites that still don’t offer IPv6 connectivity.

His list includes well-known entries like twitter.com, azure.com, and github.com plus a few unexpected ones. I find cloudflare.net not having an AAAA DNS record truly hilarious. Someone within the company that flawlessly provided my website with IPv6 connectivity for years obviously still has some reservations about their own dogfood ;)

I decided not to get involved in the EVPN-versus-LISP debates anymore; I’d written everything I had to say about LISP. However, I still get annoyed when experienced networking engineers fall for marketing gimmicks disguised as technical arguments. Here’s a recent one:

Dmitry Perets wrote an excellent description of how typical firewall cluster solutions implement control-plane high availability, in particular, the routing protocol Graceful Restart feature (slightly edited):

Most of the HA clustering solutions for stateful firewalls that I know implement a single-brain model, where the entire cluster is seen by the outside network as a single node. The node that is currently primary runs the control plane (hence, I call it single-brain). Sessions and the forwarding plane are synchronized between the nodes.

A long-time friend sent me this question:

I would like your advice or a reference to a security framework I must consider when building a green field backbone in SR/MPLS.

Before going into the details, keep in mind that the core SR/MPLS functionality is not much different than the traditional MPLS:

netlab release 1.8.1 added a interesting few features, including:

• OSPFv3 in VRFs, implemented on Arista EOS, Cisco IOS, Cisco IOS-XE, FRR, and Junos (vMX, vPTX, vSRX).
• EBGP sessions over IPv4 unnumbered and IPv6 LLA interfaces on Arista EOS
• Cisco IOS XRd container support
• Retry tests until the timeout functionality in netlab validate.

This time, most of the work was done behind the scenes¹.

Another cybersecurity rant worth reading: cybersecurity is broken due to lack of consequences.

Bonus point: pointer to RFC 602 written in December 1973.

Dan left an interesting comment on one of my previous blog posts:

It strikes me that the entire industry lost out when we didn’t do SPB or TRILL. Specifically, I like how Avaya did SPB.

Oh, we did TRILL. Three vendors did it in different proprietary ways, but I’m digressing.

Here’s another challenge for BGP aficionados: build an MPLS-based transit network without BGP running on core routers.

That should be an easy task if you configured MPLS in the past, so try to spice it up a bit:

• Use SR/MPLS instead of LDP
• Do it on a platform you’re not familiar with (hint: Arista vEOS is a bit different from Cisco IOS)
• Try to get it running on FRR containers.

In this series of blog posts, we’ll explore numerous routing protocol designs that can be used to implement EVPN-with-VXLAN L2VPNs in a leaf-and-spine data center fabric. Every design will come with a companion netlab topology you can use to create a lab and explore the behavior of leaf- and spine switches.

Our leaf-and-spine fabric will have four leaves and two spines (but feel free to adjust the lab topology fabric parameters to build larger fabrics). The fabric will provide layer-2 connectivity to orange and blue VLANs. Two hosts will be connected to each VLAN to check end-to-end connectivity.