Category: BGP

Last year I got into somewhat-heated discussion with a few engineers who followed the advice to run IBGP EVPN address family on top of an EBGP underlay.

My main argument was simple: this is not how BGP was designed and how it’s commonly used, and twisting it this way requires a schizophrenic BGP routing process, which introduces unnecessary complexity (even though it looks simple in Junos configuration) and might confuse people who have to run the network after the brilliant designer is gone.

Jon Langemak is on a writing spree: after completing his MPLS-on-Junos series he started a deep dive into ExaBGP. Well worth reading if you’re enjoying detailed technical blog posts.

Every now and then someone tells me I should write more about the basic networking concepts like I did years ago when I started blogging. I’m probably too old (and too grumpy) for that, but fortunately I’m no longer on my own.

Over the years ipSpace.net slowly grew into a small community of networking experts, and we got to a point where you’ll see regular blog posts from other community members, starting with Using BGP as High-Availability protocol written by Nicola Modena, member of ExpertExpress team.

Here’s another interesting talk from RIPE77: Routing Attacks in Cryptocurrencies explaining how BGP hijacks can impact cryptocurrencies.

TL&DR: Bitcoin is not nearly decentralized enough to be resistant to simple and relatively easy BGP manipulations.

A few years ago I got cornered by an enthusiastic academic praising the beauties of his cryptography-based system that would (after replacing the whole Internet) solve all the supposed woes we’re facing with BGP today.

His ideas were technically sound, but probably won’t ever see widespread adoption – it doesn’t matter if you have great ideas if there’s not enough motivation to implementing them (The Myths of Innovation is a mandatory reading if you’re interested in these topics).

The next set of Leaf-and-Spine Fabric Myths listed by Evil CCIE focused on BGP:

BGP is the best choice for leaf-and-spine fabrics.

I wrote about this particular one here. If you’re not a BGP guru don’t overcomplicate your network. OSPF, IS-IS, and EIGRP are good enough for most environments. Also, don’t ever turn BGP into RIP with AS-path length serving as hop count.

As I explained in a previous blog post, most leaf-and-spine best-practices (as in: what to do if you have no clue) use BGP as the IGP routing protocol (regardless of whether it’s needed) with the same AS number shared across all spine switches to implement valley-free routing.

This design has an interesting consequence: when a link between a leaf and a spine switch fails, they can no longer communicate.

You might have noticed that almost every BGP as Data Center IGP design uses the same AS number on all spine switches (there are exceptions coming from people who use BGP as RIP with AS-path length serving as hop count… but let’s not go there).

There are two reasons for that design choice:

Reading academic articles about Internet-wide routing challenges you might stumble upon valley-free routing – a pretty important concept with applications in WAN and data center routing design.

If you’re interested in the academic discussions, you’ll find a pretty exhaustive list of papers on this topic in the Informative References section of RFC 7908; here’s the over-simplified version.

In recent Software Gone Wild episodes we explored emerging routing protocols trying to address the specific needs of highly-meshed data center fabrics – RIFT and OpenFabric. In Episode 92 with Dinesh Dutt we decided to revisit the basics trying to answer a seemingly simple question: do we really need new routing protocols?