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iljitsch.com

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These are all posts about BGP, including those originally published on BGPexpert.com.

→ Software Engineering Radio: Iljitsch van Beijnum on Internet Routing and BGP

I love podcasts. So I'm every happy to be interviewed about BGP on Software Engineering Radio:

Iljitsch van Beijnum, author of the book BGP: Building Reliable Networks with the Border Gateway Protocol https://www.oreilly.com/pub/au/970 discusses internet routing and BGP – the border gateway protocol used by ISPs to update routing information. Host Robert Blumen spoke with Iljitsch about the topology of the internet, autonomous systems (AS), regulatory bodies that coordinate the AS space, IP addresses, the assignment of IPs to ASs; tier-one ISPs, carriers, and home/business ISPs; Internet routing; the path of a packet; routing tables, what they contain, and how they are constructed; routing algorithms; BGP and its role in updating routers with the knowledge of routes held by other routers; and BGP messages. Drill down into the update message. How updates progress from BGP into routing algorithms and then routing tables. What can go wrong. Attacks on BGP.

Permalink - posted 2021-07-13

→ BGP expert test v2.0!

Someone pointed out that the BGP expert test I've had on BGPExpert.com for a very long time didn't work anymore. I fixed that, and also changed a few questions. So I think I can now call it the BGP expert test v2.0.

Check it out and tell me your score!

Permalink - posted 2021-05-15

The effectiveness of AS path prepending

In a recent blog post The Effectiveness of AS Path Prepending (1) Russ White asks:

Just about everyone prepends AS’ to shift inbound traffic from one provider to another—but does this really work?

(AS path prepending means making the network path as BGP sees it longer to make a path less attractive so traffic will flow over another, shorter path.)

That's an interesting question, as I've been telling people for a long time that it often works too well.

Full article / permalink - posted 2021-05-13

Hunting down the stuck BGP routes

Ben Cox (Benjojo) has an interesting post about stuck BGP routes and a flaw in many BGP implementations where they hang when their neighbor stops accepting data over TCP: Hunting down the stuck BGP routes

A stuck BGP route means that a prefix was advertised at some point, and then it's withdrawn but the withdrawal somehow gets lost somewhere, so part of the internet still sees the withdrawn route.

Full article / permalink - posted 2021-04-22

No joke: running BGP on a $100 home router / Wi-Fi access point

For some time, I've been hearing about Mikrotek routers, which couple being quite capable with being affordable. But I never got my hands on one. I'm now in the process of upgrading my home network, and learned about the Mikrotik hAP ac³. The ac³ defies easy classification, but I think it's mostly a home router and/or Wi-Fi access point. I paid € 95 and shipping, and I believe it's available in the US for about $100.

I was somewhat disappointed to learn that "5 gigabit ports" doesn't mean ports that are capable of 5 gigabit, but 5 ports that just ordinary 1 Gbps Ethernet. Initially it seemed the box didn't support IPv6, but it turns you have to enable that under "packages" and then reboot. (Not shutdown.)

However, I wasn't disappointed to learn that the ac³ supports RIP, OSPF and BGP, both for IPv4 and IPv6.

Full article / permalink - posted 2021-04-01

When the BGP table hits 1 million prefixes, will history repeat itself?

On the APNIC blog, Danny Pinto asks What will happen when the routing table hits 1024k? Back in 2014, the IPv4 BGP table reached 512k, a common limit in many routers at the time, and some bad things happened. See my post BGP table hitting 512k limit in older routers. And pretty much the same thing happened in 2008, when the BGP table hit 256k.

Full article / permalink - posted 2021-03-23

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