Linux Networking – Source IP address selection

Any network device, be it a transit router or a host, usually has multiple IP addresses assigned to its interfaces. One of the first things we learn as network engineers is how to determine which IP address is used for the locally-sourced traffic. However, the default scenario can be changed in a couple of different ways and this post is a brief documentation of the available options.

The Default Scenario

Whenever a local application decides to connect to a remote network endpoint, it creates a network socket, providing a minimal amount of details required to build and send a network packet. Most often, this information includes a destination IP and port number as you can see from the following abbreviated output:

$ strace -e trace=network curl http://example.com
socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) = 6
setsockopt(6, SOL_TCP, TCP_NODELAY, [1], 4) = 0
setsockopt(6, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
setsockopt(6, SOL_TCP, TCP_KEEPIDLE, [60], 4) = 0
setsockopt(6, SOL_TCP, TCP_KEEPINTVL, [60], 4) = 0
connect(6, {sa_family=AF_INET, sin_port=htons(80), sin_addr=inet_addr("93.184.216.34")}, 16)

While this output does not show the DNS resolution part (due to getaddrinfo() not being a syscall), we can see that the only user-specific input information provided by an application ( Continue reading

What Would You Do With A 16.8 Million Core Graph Processing Beast?

If you look back at it now, especially with the advent of massively parallel computing on GPUs, maybe the techies at Tera Computing and then Cray had the right idea with their “ThreadStorm” massively threaded processors and high bandwidth interconnects. …

The post What Would You Do With A 16.8 Million Core Graph Processing Beast? first appeared on The Next Platform.

What Would You Do With A 16.8 Million Core Graph Processing Beast? was written by Timothy Prickett Morgan at The Next Platform.

Hedge 193: Network Automation with the Network Automation Forum

Year after year network engineering media, vendors, and influencers talk about the importance of network automation—and yet according to surveys, most network operators still have not automated their network operations. In this episode of the Hedge, part 1 of 2, Chris Grundemann and Scott Robohn join the Hedge to give their ideas on why network automation isn’t happening, and how we can resolve the many blockers to automation.

download

To find out more about the Network Automation Forum and their upcoming meeting, check out their web site.

Calico monthly roundup: August 2023

Welcome to the Calico monthly roundup: August edition! From open source news to live events, we have exciting updates to share—let’s get into it!

 

*NEW* The State of Calico Open Source: Usage & Adoption Report 2023

Get insights into Calico’s adoption across container and Kubernetes environments, in terms of platforms, data planes, and policies.

Read the report.

Customer case study: HanseMerkur

Using Calico, HanseMerkur was able to reduce infrastructure overhead and achieve organizational compliance. Read our new case study to find out how.

Get case study.

Open source news

  • Calico Live – Join the Calico community every Wednesday at 2:00 pm ET for a live discussion about learning how to leverage Calico and Kubernetes for networking and security. We will explore Kubernetes security and policy design, network flow logs and more. Join us live on LinkedIn or YouTube.
  • CNCF webinar – Watch the recording of our CNCF live webinar, where we talk about eBPF advantages and troubleshooting. Watch now.
  • Calico for Microsoft Azure – Learn technical differences between different Azure networking options for Microsoft AKS environments and tradeoff analysis. Read blog post.
  • Podcast – Listen to this joint podcast with Calico Big Cat, Parth Goswami, where they answer the Continue reading

Heavy Networking 697: Getting Operational Visibility Into The Networks That Matter (Sponsored)

In today's sponsored Heavy Networking we explore new features in Cisco Thousand Eyes, an operational tool based on visibility and observability of public and private network. Thousand Eyes has continued to grow into complex operational areas such AWS Network Path, Webex performance, and integrations with Meraki to help you identify and fix network and application performance problems.

Heavy Networking 697: Getting Operational Visibility Into The Networks That Matter (Sponsored)

In today's sponsored Heavy Networking we explore new features in Cisco Thousand Eyes, an operational tool based on visibility and observability of public and private network. Thousand Eyes has continued to grow into complex operational areas such AWS Network Path, Webex performance, and integrations with Meraki to help you identify and fix network and application performance problems.

The post Heavy Networking 697: Getting Operational Visibility Into The Networks That Matter (Sponsored) appeared first on Packet Pushers.

Dell Making The Most Of Its GPU Allocations, Like Everyone Else

In a world where Nvidia is allocating proportional shares of its GPU hotcakes to all of the OEMs and ODMs, companies like Dell, Hewlett Packard, Lenovo, and Supermicro get their shares and then they turn around and try to sell systems using them at the highest possible price. …

The post Dell Making The Most Of Its GPU Allocations, Like Everyone Else first appeared on The Next Platform.

Dell Making The Most Of Its GPU Allocations, Like Everyone Else was written by Timothy Prickett Morgan at The Next Platform.

Overcoming the Wall

I was watching a Youtube video this week that had a great quote. The creator was talking about sanding a woodworking project and said something about how much it needed to be sanded.

Whenever you think you’re done, that’s when you’ve just started.

That statement really resonated with me. I’ve found that it’s far too easy to think you’re finished with something right about the time you really need to hunker down and put in extra effort. In running they call it “hitting the wall” and it usually marks the point when your body is out of energy. There’s often another wall you hit mentally before you get there, though, and that’s the one that needs to be overcome with some tenacity.

The Looming Rise

If your brain is like mine you don’t like belaboring something. The mind craves completion and resolution. Once you’ve solved a problem it’s done and finished. No need to continue on with it once you’ve reached a point where it’s good enough. Time to move on to something else that’s new and exciting and a source of dopamine.

However, that feeling of being done with something early on is often a false sense of completion. Continue reading

Improving Worker Tail scalability

Improving Worker Tail scalability
Improving Worker Tail scalability

Being able to get real-time information from applications in production is extremely important. Many times software passes local testing and automation, but then users report that something isn’t working correctly. Being able to quickly see what is happening, and how often, is critical to debugging.

This is why we originally developed the Workers Tail feature - to allow developers the ability to view requests, exceptions, and information for their Workers and to provide a window into what’s happening in real time. When we developed it, we also took the opportunity to build it on top of our own Workers technology using products like Trace Workers and Durable Objects. Over the last couple of years, we’ve continued to iterate on this feature - allowing users to quickly access logs from the Dashboard and via Wrangler CLI.

Today, we’re excited to announce that tail can now be enabled for Workers at any size and scale! In addition to telling you about the new and improved scalability, we wanted to share how we built it, and the changes we made to enable it to scale better.

Why Tail was limited

Tail leverages Durable Objects to handle coordination between the Worker producing messages and Continue reading

Event-Driven Ansible – ChatOps – From Chat to Action

Like any well-rounded individual, in times of intense concentration, you will find me talking to myself in search of some hidden knowledge that I might have received in a dream, or perhaps quoting something from a fantasy novel about wizards and creatures in an attempt to fix a problem. Unfortunately, wearing a robe and shouting “Repairo Network!” while pointing my pen toward the device has yet to help in any situation. 

At the 2023 AnsibleFest, as part of the main stage demonstration, I used the magic of Event-Driven Ansible to integrate ChatOps in our fictional infrastructure drama. ChatOps is not new, but I think it's a pretty cool way to make changes or interact with your infrastructure. 

We know that Event-Driven Ansible requires a source for events, a list of conditions which we call rulesets, and ultimately an action to match those conditions, which makes it perfect to use as a chatbot-type system.

For me to have a heart-to-heart with my beloved network, I will need to configure my chat as a source of events for Event-Driven Ansible, and to do this, I will use the webhook source plugin, which is part of the ansible.eda collection. Continue reading

Nexus9000v and “Missing” Routes

I have built my lab for VXLAN on the Nexus9300v platform. Since I have a leaf and spine topology, there are ECMP routes towards the spines for the other leafs’ loopbacks. When performing labs though, I noticed that I didn’t have any ECMP routes in the forwarding table (FIB). They are in the RIB, though:

Leaf1# show ip route 203.0.113.4
IP Route Table for VRF "default"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%<string>' in via output denotes VRF <string>

203.0.113.4/32, ubest/mbest: 2/0
    *via 192.0.2.1, Eth1/1, [110/81], 1w0d, ospf-UNDERLAY, intra
    *via 192.0.2.2, Eth1/2, [110/81], 1w0d, ospf-UNDERLAY, intra

There is only one entry in the FIB, though:

Leaf1# show forwarding route 203.0.113.4?
  A.B.C.D      Display single longest match route
  A.B.C.D/LEN  Display single exact match route

Leaf1# show forwarding route 203.0.113.4/32

slot  1
=======


IPv4 routes for table default/base

------------------+-----------------------------------------+----------------------+-----------------+-----------------
Prefix            | Next-hop                                | Interface            | Labels          | Partial Install 
------------------+-----------------------------------------+----------------------+-----------------+-----------------
203.0.113.4/32       192.0.2.1                                 Ethernet1/1

This seemed strange to me and I was concerned that maybe something was Continue reading

Lifetime ipSpace.net Subscription

More than thirteen years after I started creating vendor-neutral webinars, it’s time for another change1: the ipSpace.net subscriptions became perpetual. If you have an active ipSpace.net subscription, it will stay valid indefinitely2 (and I’ll stop nagging you with renewal notices).

Wow, Free Lunch?

Sadly, that’s not the case.

Read more …

Lifetime ipSpace.net Subscription

More than thirteen years after I started creating vendor-neutral webinars, it’s time for another change1: the ipSpace.net subscriptions became perpetual. If you have an active ipSpace.net subscription, it will stay valid indefinitely2 (and I’ll stop nagging you with renewal notices).

Wow, Free Lunch?

Sadly, that’s not the case.

Read more …

Cloudflare Radar’s 2023 overview of new tools and insights

Cloudflare Radar’s 2023 overview of new tools and insights
Cloudflare Radar’s 2023 overview of new tools and insights

Cloudflare Radar was launched in September 2020, almost three years ago, when the pandemic was affecting Internet traffic usage. It is a free tool to show Internet usage patterns from both human and automated systems, as well as attack trends, top domains, and adoption and usage of browsers and protocols. As Cloudflare has been publishing data-driven insights related to the general Internet for more than 10 years now, Cloudflare Radar is a natural evolution.

This year, we have introduced several new features to Radar, also available through our public API, that enables deeper data exploration. We’ve also launched an Internet Quality section, a Trending Domains section, a URL Scanner tool, and a Routing section to track network interconnection, routing security, and observed routing anomalies.

In this reading list, we want to highlight some of those new additions, as well as some of the Internet disruptions and trends we’ve observed and published posts about during this year, including the war in Ukraine, the impact of Easter, and exam-related shutdowns in Iraq and Algeria.

We also encourage everyone to explore Cloudflare Radar and its new features, and to give you a partial review of the year, in terms of Internet Continue reading

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