Monday, April 29, 2024

Solved: Error: eth0 interface name is not allowed for R2 node when network mode is not set to none in containerlab


   Containerlab returns a similar error:

Error: eth0 interface name is not allowed for R2 node when network mode is not set to none


 In the .yml file in the node section indicating the topology error specify:

network-mode: none








      kind: linux


      network-mode: none

 Rerun the topology with clab dep -t file.yml and that's it!


Friday, March 8, 2024

BGP Stream: An Analysis of One Year of BGP Incidents


By Alejandro Acosta, R&D Coordinator at LACNIC

LACNIC presents the first webpage designed to show incidents and an analysis of Border Gateway Protocol (BGP) measurement data in Latin America and the Caribbean.

MAIN INCIDENTS. In addition to a summary of the information, the page shows three main types of events: possible network hijacks, BGP outages, and route leaks.

Possible hijacks refers to the illegitimate takeover of groups of IP addresses by corrupting Internet routing tables. This typically occurs when an Autonomous System announces a prefix that it does not originate.

Outages refers to the loss of visibility of network prefixes by a majority group of sensors.

Route leaks, as the name suggests, refers to the —potentially— unintentional announcement of a network prefix via BGP. For example, in a private peering traffic exchange, when one of the participants announces the peer’s prefix to the Internet. This case is the most difficult for algorithms to detect, so some of these incidents are not identified.

How is the data obtained?

This initiative uses Cisco BGP Stream, an automated process that selects the largest and most important incidents, providing information on the nature of the event and the ASNs involved.

The information is openly published, as LACNIC believes that it is important for engineers, network administrators, and organizations to gain insights into the most common incidents in the region and raise awareness about the situation.

This allows quickly investigating events, the rapid development of complex prototypes and tools, as well as large-scale monitoring applications (e.g., detecting connectivity outages, attacks, or BGP hijacks).

Using a system developed by LACNIC’s R&D department, raw data is collected, plotted, identified, cleaned, stored in a database, and later used to produce statistics and graphs. This occurs automatically every 24 hours.

RESULTS. During the study period —February 2023 to February 2024— we found the results shown in the charts below, which compare BGP events worldwide vs BGP events in our region.

A comparison between the global chart and the chart specific to the LAC region shows a similar pattern in the order of the most common incidents, with outages being the most frequent type of incident, followed by possible hijacks, and finally prefix leaks. It should also be noted that outages represent a higher percentage of the total number of incidents in our region than at the global level.

An analysis of the results table showing worldwide BGP events vs BGP events in our region reveals the following:

TOP 5 countries in our region with the highest number of BGP outages


TOP 5 countries in our region with the highest number of possible Hijacks

Expected CCDetected CCEvents

TOP 3 countries in our region with the highest number of route leaks

Origin CCLeaker CCEvents


In this first year of operation, LACNIC has observed a reduction in BGP incidents. Several reasons for this have been identified, including a) the deployment and adoption of Resource Certification (RPKI), b) LACNIC’s Internet Routing Registry (IRR), and the adoption of RFC 9234 (Route Leak Prevention and Detection Using Roles in UPDATE and OPEN Messages).

The adoption of these tools is being driven by better operator practices and ISOC’s promotion of MANRS.


Possible hijacks, outages, and route leaks are the most common types of BGP incidents. During the initial year of data collection, a decrease in the number of cases was observed. However, it is expected that they will not disappear entirely in the near future. Implementing robust redundancy and resiliency measures in networks is crucial, as is the early detection and prevention of possible hijacks to ensure the integrity and reliability of Internet routes.

At LACNIC, our goal is to raise awareness and encourage ISPs and organizations to be prepared to handle these incidents efficiently when they occur.


Tuesday, February 27, 2024

This is the way to install the telnet command in Alpine Linux (very popular in the container world such as docker)

This is the way to install the telnet command in Alpine Linux (very popular in the container world such as docker)

#apk update

#apk add busybox-extras

Friday, February 23, 2024

The real solution to run ContainerLAB on MAC m1 or m2 apple silicon

Step 1: Install Canonical Multipass your MAC 

$brew install multipass

Step 2: Install the VM called docker

$multipass launch docker --name mydocker

Step 3: Connect to the new VM

$multipass shell mydocker

Step 4: Inside the VM install ContainerLab

$sudo su

#bash -c "$(curl -sL"

Let's try this simple back2back topology of two Linux computers with FRR

-- 2-frr-back2back.yml --

name: ipv6-ws





   do not give:

   ROUTERS ###


       kind: linux



         - "sysctl -w net.ipv6.conf.all.forwarding=1"

         - "ip address add dev eth1 2001:db8:ffab::1/64"


       kind: linux



         - "ip address add dev eth1 2001:db8:ffab::2/64"

         - "sysctl -w net.ipv6.conf.all.forwarding=1"


     - endpoints: ["R1:eth1", "R2:eth1"]

--- yml --

Step 5: Let's build the topology with clab:

clab dep -t 2-frr-back2back.yml

Step 6: finally we are going to connect to one of the VMs inside ContainerLAB

docker exec -i -t clab-ipv6-ws-R2 bash

Thursday, February 1, 2024

A Much-Needed BGP RFC: AS Path Prepending


The Border Gateway Protocol (BGP) plays a critical role in building and maintaining Internet routing tables, so much so that it is considered the “glue” that holds the Internet together. In this context, a long-standing and very popular technique known as ‘AS Path Prepending’ has been devised as a key strategy for influencing route selection and optimizing an AS’s inbound and outbound traffic.

In this document, we will navigate through the IETF draft titled “AS Path Prepending” [1], which includes several ideas and concepts that are of great value to the community.

About draft-ietf-grow-as-path-prepending

This draft has been under discussion within the Global Routing Operation (GROW) Working Group since 2020 and is currently on version 10. The document has seven co-authors: M. McBride, D. Madory, J. Tantsura, R. Raszuk, H. Li., J. Heitz, and G. Mishra. It predominantly received support on the discussion list (including my own). You can read the draft here.

What is AS Path Prepending?

AS Path Prepending is a technique that involves repetitively adding one’s autonomous system identifier (ASN) to the list of ASs in a BGP route path (AS_PATH). Its goal is to influence route selection by making certain paths less attractive to inbound/outbound traffic. In other words, it consists of adding our autonomous system to the AS_PATH and therefore artificially “lengthening the path” to a prefix on the Internet.

In the figure above, without prepends, Router A prefers to go to C via B. However, when three prepends are added on B, router A decides to reach C via D.

Why is AS Path Prepending used and what is it used for?

AS Path prepending is used for multiple reasons. The main reason is undoubtedly traffic engineering, which in turn is used to influence an AS’s inbound and outbound traffic. It is very likely that the AS wishes to achieve one of the following goals:

  • to distribute traffic among two or more upstream providers, or
  • to have an upstream backup provider.
  • Whatever the case, the goal is traffic engineering.

To prepend or not to prepend, that is the question

Prepending is a bit like NAT in that it is often a necessary evil. As we will explain, its excessive and sometimes unnecessary use can become a vulnerability with significant implications for network stability.

What’s wrong with using AS Path Prepending?

We all know that AS Path Prepending is a very common technique to influence BGP decisions. However, its excessive, incorrect, and sometimes unnecessary use can have negative consequences. For example:

  • Creation of suboptimal traffic flows. In other words, we may achieve our goal of distributing traffic in the immediate links; however, beyond our immediate upstream, traffic is not optimized to reach our autonomous system and vice versa.
  • Prefix de-aggregation. When implementing traffic engineering, it is very common to de-aggregate prefixes, which affects the Internet ecosystem.
  • In the event of a route-leak, under normal circumstances, the as-path of our advertisements would be shorter than that of the leaked route. However, if we artificially lengthen the path by prepending, the as-path of the leaked routes may be shorter than those we are legitimately announcing for our legitimate prefix, which would have lower preference, leading to potential route hijacking, attacks, and a long etcetera.
  • Memory consumption. As expected, these AS Path Prepends are learned by BGP Speakers, thus increasing their memory usage. To this I would add that prepending introduces a small additional CPU usage penalty for each prefix.

Given that AS Path Prepend is no longer recommended, what alternatives are available?

There are many techniques for performing traffic engineering in BGP. I will mention some that appear in the draft:

  • Leveraging BGP communities. In addition to the well-known BGP communities, I recommend talking to your BGP peers to optimize traffic. There are numerous BGP communities implemented by providers, which might certainly benefit your setup.
  • Announcing more specific routes to your main upstreams.
  • Manipulating the AS Origin Code. Remember that this attribute is also found in the BGP route selection algorithms.
  • Using Multi Exit Discriminator (MED), a non-transitive attribute that can be used with excellent results for manipulating inbound traffic when we have several links to the same provider
  • Using Local-Preference, another non-transitive attribute, perfect for influencing the traffic that leaves our autonomous system

This is all well and good, but I still need to use AS Path Prepending. Any suggestions?

The draft mentions the best current practices when using AS Pat Prepending, which I will summarize below:

  1. Only use AS Path Prepending if it is absolutely necessary.
  2. Due to some traffic manipulation techniques, when using AS Path Prepending, we may not see significant changes in the traffic distribution, which is why it is important to talk to our peers to see if they will honor the prepends.
  3. Use local-preference on our network.
  4. Don’t prepend ASNs that you don’t own.
  5. Don’t prepend if you are connected to a single ISP using a single link, i.e., single homed (this one is not included in the draft).
  6. If we prepend a prefix, it might not be necessary to use that prepend for all our peers.
  7. There is no need to use more than five prepends. The reason for this is that more than 90% of path are five ASs or fewer in length.

Final Considerations

The use of AS Path Prepending is a valuable strategy but should be used only when necessary and with caution, following best practices. Excessive use of prepends may cause unforeseen events that may affect our autonomous system from a traffic and a security perspective.

We invite you to read the full draft (available here and to join the discussion on the LACNOG mailing list.

We also encourage you to comment on this post to let us know if you are prepending your ASN, as well as why and what you are using this for.



Monday, January 8, 2024

Two very short jokes, one TCP and other UDP


 ” You wanna hear a TCP joke ?
 You wanna hear a TCP joke ?
 You wanna hear a TCP joke ?
 You wanna hear a TCP joke ?



I’d tell you a UDP joke, but you might not get it.