What is Internet Exchange Point (IXP)

Most people know about Internet Service Providers (ISP). People must subscribe to at least one ISP to connect to the Internet. Operating behind the scenes, specialized network infrastructures play a crucial role in ensuring the Internet works correctly and efficiently. This role is the Internet Exchange Point (IXP). In this post, I will explain in greater depth why we need this new role, and what problem this role solves.

Independent ISPs without direct connections

BGP Millionaire

【 BGP Millionaire】

I used this tool to generate this plot.
Plot Range: 01-Feb-2025 0001 to 30-Apr-2025 0030.

Recently I observed and noticed that, global IPv4 BGP table size has already grown over 1 million entries, around February to April time in this year, 2025.

BGP AS-Path Filtering, Demonstration

How many of you are working with BGP in your daily job? Let me know in the comments below this post.

I also created a live demonstration about filtering based on BGP AS-Path with Regular Expressions. I hope it is helpful to you.

Breaking 100K Entries is the Global IPv6 BGP Table

This year, 2020, around November I started to see the global IPv6 BGP Table is getting more than 100K entries. Although the number is going above and under 100K from time to time, starting from the end of November I can safely say it is breaking 100K entries right now.

This is an interesting milestone for IPv6. That means a massive majority of people are using IPv6 today. I want to note down this moment. And I want to share 3 of my own observations about the IPv6 BGP table.

Global BGP IPv4 table is around 800K in size

This week the global BGP IPv4 table is around 800,000 entries in size. I bring this up just to give you a head-up and say a “Wow”. I don’t want to make you worry about the number. This is not my intention.

I still remember the “old good time” when I had installed a BGP router (Cisco 3660) with 256 Megabytes of DRAM memory in year 2001. At that time, the BGP table is below 150,000 entries so that router worked well.

BGP Injection instead of Leak, my observation notes for MyEtherWallet incident

After reading articles by Doug Madory, and by Louis Poinsignon, here are some notes I observed and learned.

[What happened in this incident?]

Hackers somehow made some BGP routers of “eNet” to falsely announce that they own the following 5 IP subnets, which are indeed NOT belonging to “eNet”. The true owner is Amazon. To be more specific, they are for Amazon’s Route 53 DNS name resolution services.

• 205.251.192.0/24
• 205.251.193.0/24
• 205.251.195.0/24
• 205.251.197.0/24
• 205.251.199.0/24

The registered domain server for domain “MyEtherWallet.com” is hosted on Amazon Route 53.

Hackers also somehow embedded malicious DNS server (or servers, I really don’t know) also inside service network of “eNet”.

After that, any affected clients’ DNS query for domain “MyEtherWallet.com” would hit hacker’s malicious DNS server. Of course, malicious DNS server would respond with false IP addresses, and those false IP addresses are indeed hacker’s own web servers.

At this moment, clients thought they were accessing “MyEtherWallet.com”, and they indeed were accessing hacker’s web servers.

Three configuration management features I like about Cisco IOS XR

I like more and more about Cisco IOS XR after I start to play with it. Here are three quick things I like about IOS XR.

Tomato farm and yellow tomato flowers.
Photo taken in Hsinchu County, Taiwan.

Some handy commands I use to save my time doing Cisco IOS XR labs

Remember: Default behaviors of Cisco IOS XR are there to secure your router even we forget to configure them. Never try to disable them on any production network!

For lab practice, however, security is not my concern at all. I list some of my handy configuration fragments to save me time when I do IOS XR labs. I hope they are also helpful to you!

Flower of strawberry.
Photo taken in Hsinchu County, Taiwan.

A simple example explaining why we need Prefix-List in addition to simple Access-List (ACL) on Cisco IOS

My example is: assume we want to filter out "all possible subnets/prefixes inside 192.168.1.0/24" from rushing into our router.

Red House Theater, at the West Gate of Taipei Wall (西門紅樓、紅樓劇場). 

We can first visualize what subnets are to be filtered in the following, but incomplete list:

192.168.1.0/24

192.168.1.0/25
192.168.1.128/25

192.168.1.0/26
192.168.1.64/26
192.168.1.128/26
192.168.1.192/26

(and even more ...)

Propagation of BGP Routing Information among Routers belonging to the Same Company, Part 1

Hukou Old Street after sunset.
Hukou Township, Hsinchu County, Taiwan.

This post is continuing the previous BGP post.

Propagation of BGP Routing Information among Routers belonging to Different Companies

Another photo of Jih Yueh Shan Jing Leisure Farm (日月山景休閒農場).
Changhua County, Taiwan (Google Plus)

Yes! Most of the books mentioned this scenario as External BGP (sessions).

Cisco IOS IPv6 BGP configuration, using link local addresses as transportation

In this example, I am building two external BGP peering relationships. One is going from WAN and the other is going from LAN.

Source of Cisco IOS "show ip bgp" screen outputs: archive.routeviews.org

It would not be easy for us to capture meaningful BGP table in the lab environment. An archive site of "University of Oregon Route Views Project" provides us such samples of captures.

Incident details of last Friday, by RIPE NCC

This is the follow-up of last Friday's incident, by RIPE NCC.

Some Internet BGP routers reset neighbors within half an hour last Friday

We know when the BGP neighbor relation resets itself, the network would become disrupted before the new relation re-establishes. In the Intenet BGP scenario, this means a sudden outage of couple of minutes.

This was what happened last Friday (August 27, 2010, from 08:41 to 09:08 UTC)

Simple BGP Multipath Test in Packet Tracer 5.3

This is another simple BGP test file in Packet Tracer 5.3. We can see selection of the best route by AS_PATH.

BGP sample practice, in the new Packet Tracer 5.3

I created this practice to test the Packet Tracer 5.3 features of BGP.

Using "peer-group" shutdown to prepare BGP peer configurations without bothering

I was doing a BGP lab with my students.

I wanted to pre-configure some BGP neighbors, and I wanted all neighbor sessions to start at once only by some simple commands. Furthermore, I do not want to bother my students by retrying BGP neighbor connections before they completed their BGP neighbor configurations.

I came up this small trick to achieve above goals:

RAM Suggestions for most BGP Routers

Although my post provides a rough estimation about how much RAM could a BGP router take (70M bytes for 100,000 routes), I would like to suggest you to buy the maximum size of RAM of your router model in your deployment.

Number of BGP routes comes up to 300,000

I came across this post: "BGP breaks 300,000". Applying my previous rough estimation: 70M bytes for 100,000 routes, it would takes around 210M bytes to only store that 300,000 BGP routes in memory alone!