This post is going to follow a multicast packet as it moves through a sample MPLS network using Label Switched Multicast (LSM). I’ll show how the packet moves through the network by looking at the forwarding tables on different routers and also by doing some packet captures.
This post is part of a series I’m writing on LSM and if you’re not already familiar with LSM, I recommend you go back and read the previous posts.
After reading this post you will be able to precisely describe how LSM forwarding works in the data plane and will be able to do some basic troubleshooting.
Let’s get into the lab!
Continue reading Label Switched Multicast – Packet Walk
In the previous post (Label Switched Multicast – An Introduction) in this series on Label Switched Multicast (LSM) I introduced the concepts behind LSM and draft-rosen, the two most poplar methods for transporting multicast traffic through MPLS Layer 3 VPNs.
In this article I will talk through the configuration of LSM on the PE and P routers and get to the point where two CEs are successfully passing multicast traffic via the MPLS network. All of the configuration examples will be relevant to Cisco IOS.
As was the case in the introduction article in the series, it’s best if you already have a good understanding of multicast and MPLS before reading this article.
At the end of this article you’ll be able to start configuring your own LSM environment using the configuration samples here as a template.
To the CLI! Continue reading Label Switched Multicast – Configuration
There are two common methods for transporting multicast packets within an MPLS-based Layer 3 VPN:
- Generic Routing Encapsulation (GRE) with Protocol Independent Multicast (PIM) (also known as “draft-rosen”)
- Label Switched Multicast (LSM)
There’s also a third method which uses Resource Reservation Protocol—Traffic Engineering (RSVP-TE) but I’m not going to get into that one.
In this first post in a series on LSM, I’ll describe how draft-rosen works, how LSM works, and then compare and contrast the two. Subsequent posts will focus solely on LSM.
At the end of this post, you will be able to describe conceptually how the control and data planes work with LSM and what the pros and cons are of LSM as compared to draft-rosen.
I will not be covering any theory on multicast or MPLS and will instead recommend that you be familiar with both topics before reading further.
Here we go!
Continue reading Label Switched Multicast – An Introduction
Happy New Year! As is my tradition, here are the 2015 blog statistics as compared to 2014.
I’m pretty excited that once again readership and overall reach of this blog has increased by double digits. I’m looking forward to growing these numbers and creating challenging and interesting new content in 2016.
Continue reading 2015 End of Year Blog Statistics
The idea for this post came from someone I was working with recently. Thanks Fan (and Carson, and Shree) :-)
In Service Software Upgrade (ISSU) is a method of upgrading software on a switch without interrupting the flow of traffic through the switch. The conditions for successfully completing an ISSU are usually pretty strict and if you don’t comply, the hitless upgrade can all of a sudden become impacting.
The conditions for ISSU on the Nexus 5000 are pretty well documented (cisco.com link) however, there are a couple bits of knowledge that are not. This post is a reminder of the ISSU conditions you need to comply with and a call out to the bits of information that aren’t so well documented.
Continue reading Avoiding an ISSUe on the Nexus 5000
In this post I’m going to look at the characteristics of OSPF and EIGRP when used in a Dynamic Multipoint VPN (DMVPN). I will do my best not to play favorites and instead stick to the facts (yes, I do have a preference :-). To that end I will back everything up with data from my lab. The focus areas of the comparison will be:
- Scalability of the hub router’s control plane
- Overall control plane stability
- Traffic engineering
This post won’t go into any background on how DMVPN works. If you’re not yet familiar with DMVPN, I recommend watching these introductory videos by Brian McGahan. This post also does not do a deep dive on OSPF or EIGRP. I’m making the assumption that you’re already familiar with the different LSA types in OSPF and general functions of EIGRP.
After reading this post you should be able to describe the pros and cons of OSPF and EIGRP in the three areas listed above and incorporate this knowlege into a DMVPN design.
Continue reading OSPF vs EIGRP for DMVPN
Design For How People Learn, by Julie Dirksen (ISBN 978-0321768438)
I saw the title for this book roll across my Twitter feed — can’t remember from who, sorry — from someone who had a blog and was advocating for other bloggers to check this book out. When I read the abstract for the book, I immediately added it to my reading list.
“Whether it’s giving a presentation, writing documentation, or creating a website or blog, we need and want to share our knowledge with other people. But if you’ve ever fallen asleep over a boring textbook, or fast-forwarded through a tedious e-learning exercise, you know that creating a great learning experience is harder than it seems.”
Continue reading Book Review: Design For How People Learn
The oft-requested and long awaited arrival of TACACS+ support in Cisco’s Identity Services Engine (ISE) is finally here starting in version 2.0. I’ve been able to play with this feature in the lab and wanted to blog about it so that existing ISE and ACS (Cisco’s Access Control Server, the long-time defacto TACACS+ server) users know what to expect.
Below are five facts about how TACACS+ works in ISE 2.0.
Continue reading Five Functional Facts about TACACS+ in ISE 2.0
I will be presenting at the Cisco Connect Canada tour in Edmonton and Calgary on November 3rd and 5th, respectively. My presentation is about that three letter acronym that everyone loves to hate: SDN :-)
I will talk about SDN in general terms and describe what it really means; what we’re really doing in the network when we say that it’s “software defined”. No unicorns or fairy tales here, just engineering.
Next I’ll talk about three areas where Cisco is introducing programmability into its data center solutions:
- Application Centric Infrastructure
- Virtual Topology System
- Open NX-OS
Below are the notes I made for myself while researching these topics and preparing for the presentation. At the bottom of this post is a Q&A section with some frequently asked questions.
Continue reading Speaking Notes: The Data Center Network Evolution
At the time that I’m writing this I’ve been working at Cisco for just over 3 years as a Systems Engineer. Prior to that I worked for multiple Cisco customers and was heavily involved in Cisco technologies. I know what a monster cisco.com is and how hard it can be to find what you’re looking for.
Since starting at Cisco, the amount of time I’ve spent on cisco.com has shot up dramatically. Add to that studying for my CCIE and it goes up even more. In fact, cisco.com is probably the number 1 or 2 site I visit on a daily basis (in close competition with Google/searching).
After spending all this time on the site and given how vast the site is and how hard it can be to find that specific piece of information you’re looking for, I’m writing this post as an aid to help other techies, like myself, use the site more effectively.
Continue reading How a Cisco SE Navigates Cisco.com