BGP Communities
BGP Communities has to be one of my favorite features added to the BGP protocol. As you should know by now, BGP passes several attributes between peers that help influence the BGP best path selection algorithm. One of these is the BGP Community attribute. Think of this as another tag placed on the route advertisement that can give us additional information.
This tag is formatted as 32bit value that is typically displayed in two 16 bit parts. The most typical, and most widely accepted best practices treat these as your Autonomous System Number (ASN), followed by a 16 bit attribute. For example, if your ASN was 65248 and you wanted to tag this route with the number 666, you would set something like 65248:666.
As for the second half of our tag, this number is arbitrary. BGP Communities are a transitive attribute that is completely optional. This means that BGP treats these tags as purely information, and that it is up to the network engineer to decide what these values mean, and what to do with them.
RFC 1997 defines some well known communities that have global significance. These values and their operations should be respected by any community Continue reading
My First Week at Cumulus Networks
From the first time I spoke with someone at Cumulus Networks, I realized I’d come across something spectacular. My interviews started with a “screening” call from Nat Morris, but it didn’t start with any of those awkward “tell me about yourself” ice-breaker questions. Nat immediately began the conversation with a detailed description of the Cumulus Workbench, his plans for where to take it, and what I thought about them. For someone like me, being able to talk candidly about a concrete project made it easy for me to see myself in the position, and I felt like I was being treated as if I were already a part of the company. This conversation left such a powerful impression that it literally carried me through the entire interview process.
I started on the day before the RDU team moved from the Apex office to the new office in Cary. All of the furniture was gone, everyone was huddled at folding card tables, and I ended up sitting on the floor in another room since we didn’t have enough chairs even after borrowing some from the restaurant next door! The team assured me that it wasn’t a bait-and-switch by showing me Continue reading
The Packet Flow Duality
Quantum physics is a funny thing. It seeks to solve all the problems in the physical world by breaking everything down into the most basic unit possible. That works for a lot of the observable universe. But when it comes to light, quantum physics has issues. Thanks to experiments and observations, most scientists understand that light isn’t just a wave and it’s not just a collection of particles either. It’s both. This concept is fundamental to understanding how light behaves. But can it also explain how data behaves?
Moving Things Around
We tend to think about data as a series of discrete data units being pushed along a path. While these units might be frames, packets, or datagrams depending on the layer of the OSI model that you are operating at, the result is still the same. A single unit is evaluated for transmission. A brilliant post from Greg Ferro (@EtherealMind) sums up the forwarding thusly:
- Frames being forwarded by MAC address lookup occur at layer 2 (switching)
- Packets being forwarded by IP address lookup occur at layer 3 (routing)
- Data being forwarded at higher levels is a stream of packets (flow forwarding)
It’s simple when you think Continue reading
VXLAN on VMware NSX: VTEP, proxy, Unicast/Multicast/Hybrid mode
Virtual Extensible LAN (VXLAN) is a network which help to build an overlay network and it’s the base of network virtualization. In simple words, VXLAN encapsulates Ethernet frames on a UDP routable packet. With VXLAN a single L2 segment can span L3 boundaries. Moreover VXLAN overcomes VLAN limits: 802.1q standard define a maximum of 4094 […]HTIRW: The IETF Draft Process
In our deeper investigations of the IETF as a “sample standards body” in this (apparently forever running) series on how the Internet really works, let’s take a look at the IETF standards process. This is a rather sanitized, informal review — I may leave out some steps, or describe things in a way that doesn’t […]
Author information
The post HTIRW: The IETF Draft Process appeared first on Packet Pushers Podcast and was written by Russ White.
Kubernetes 101 – The constructs
In our last post, we got our base lab up and running. In this post, I’d like to walk us through the four main constructs that Kubernetes uses. Kubernetes defines these constructs through configuration files which can be either YAML or JSON. Let’s walk through each construct so we can define it, show possible configurations, and lastly an example of how it works on our lab cluster.
Pods
Pods are the basic deployment unit in Kubernetes. A pod consists of one or more containers. Recall that Kubernetes is a container cluster management solution. It concerns itself with workload placement not individual container placement. Kubernetes defines a pod as a group of ‘closely related containers’. Some people would go as far as saying a pod is a single application. I’m hesitant of that definition since it it seems too broad. I think what it really boils down to is grouping containers together that make sense. From a network point of view, a pod has a single IP address. Multiple containers that run in a pod all share that common network name space. This also means that containers Continue reading
Cisco ISLB Issue
Usually people are blogging on a certain topic because they want to share they knowledge with a certain protocol or product. Today I ll take another approach with that fact and I will actually do the exact opposite. I have an issue with ISLB which allows load balancing for my iSCSI sessions. Today I will elaborate […]WLAN Capacity Planning: From Concept to Practice [Video]
Last week I presented at the Wireless LAN Professionals Conference (#WLPC) in Dallas, TX. The topic of my presentation was putting the concepts of WLAN capacity planning into practice.
Agenda:
- Factors of Network Performance (and why variable contention delay is critical to WLANs)
- Iterative WLAN Design Methodology
- Hands-On with the Revolution Wi-Fi Capacity Planner
- Real-World Example and Walkthrough (including tying capacity planning to RF planning)
The video is now available online:
If you would like a review of capacity planning concepts prior to watching the hands-on example, my presentation from last year's WLPC 2014 is also available online.
Cheers,
Andrew von Nagy
EIGRP Named Mode
Original content from Roger's CCIE Blog Tracking the journey towards getting the ultimate Cisco Certification. The Routing & Switching Lab Exam
EIGRP Named Mode or Multi-AF Mode is a new development in EIGRP starting in Version 15.x Its reason for being is to simplify the EIGRP configuration into one place, as previously with EIGRP classic version the configuration was between the interface and the global process which made it harder to see all the configuration relating... [Read More]
Post taken from CCIE Blog
Original post EIGRP Named Mode
Change switch branding from H3C to HP
If you still have some original H3C branded switches in your network, it is possible to re-brand them to HP, so they will be recognized as the HP counter-part of the H3C model. To change the brand, use the brand … Continue reading
Check Cisco ASA Connections with Nagios
Once you’ve setup your Cisco ASA, you will want to monitor it to ensure that it’s operating normally. The plugin nm_check_asa_connections for Nagios, and compatible products, can warn your if the number of current connections gets too high. A very high connection count might indicate that there’s an attack under way on one of your servers, you have some hosts on your inside which are part of a botnet and is attacking someone else, or perhaps you’re just about to grow out of your current firewall and need an upgrade to a more powerful box.