Some OpenFlow-focused startups are desperately trying to tell you how redundant their architecture is. Unfortunately all the whitepapers (and the prancing unicorns) cannot change a simple fact: an SDN controller (OpenFlow-based or otherwise) is in some aspects a single failure domain.
Read more ...Not really the line anyone wants to hear, especially after watching the Terminator films! This however isn’t what this post is about, so if you’re a bit of a rebel, fear not. No network vendor branded termination thing (maybe other than poor documentation or code) will result in your death.
Since the era of the abacus, little consideration has been given to how software that relies upon a computer network actually interacts with it. Sure, most developers know how to drive a socket library and make things happen at a session level, but almost no consideration is given by a developer on how to deploy an enterprise application to a production environment.
This post represents a set of thoughts that have been maturing over the last few months. They are very much my own thoughts and do not represent those of others. I would be interested to hear if you have the same thoughts or any interesting different takes.
Before smart phones and tablets came along, software for the domestic populous provided a means of typing and printing spell checked letters to your pen pals, figuring out your weekly shopping Continue reading
There’s nothing quite so unnerving as being laid off. I know, because I’ve been let go in a “limited restructuring” twice in my life. Through the process, I learned some “life lessons,” that apply to just about every engineering in the world. While I’m safely ensconced in a great place at Ericsson, I thought it might be useful to reflect on the lessons I’ve learned — especially as it seems to be layoff season in other places (or maybe it’s layoff season all the time?).
First, it doesn’t matter if it’s about you, the politics, or just a random event. I still harbor a suspicion that both times I was laid off there was more going on in the background than just “we don’t need your services any longer.” There were probably politics. On the other hand, the politics in these situations are always bigger than you, no matter how personal it might seem. There’s always some back story, there’s always some power play in progress, there’s always some internal struggle.
But the truth is — it doesn’t matter. You can either stew on the past, or move on with your life. Stewing in the past isn’t going Continue reading
In the first article of this series, reliability and resiliency has been explained. Every component and every device can and eventually will fail, thus system should be resilient enough to re converge/recover to a previous state. Resiliency can be achieved with redundancy. But how much redundancy is best for the resiliency is another consideration to […]
The post Common Network Design Concepts Part-2 appeared first on Packet Pushers Podcast and was written by Orhan Ergun.
One of my readers sent me an interesting challenge: they’re deploying a new DMVPN WAN, and as they cannot expect all locations to have native (non-NAT) IPv4 access, they plan to build the new DMVPN over IPv6. He was wondering whether it would work.
Apart from “you’re definitely going in the right direction” all I could tell him was “looking at the documentation I couldn’t see why it wouldn’t work” Has anyone deployed DMVPN over IPv6 in a production network? Any hiccups? Please share your experience in the comments. Thank you!
TL;DR: I'll be in Bern on September 9th. If you'd like to drop by and discuss network design or automation challenges, read on…
Read more ...At this point in the PacketU subnetting series, we have worked through the following–
This article takes the concept of subnetting to the next step. Today we are going to look at the concepts required to subnet a Class C network. As we reflect on the Classful IP rules, we recall that a Class C network has the following characteristics–
We also know that this single IP network can be further subdivided into multiple, but smaller, networks. This process is known as subnetting.
Continuing with the syntax used in previous articles, we might represent a Class C Network as follows–
192.168.100.0 In this example-- Blue represents a Classful Network Green represents a Host address
In this case the host address value is 0, so only the network is being represented here. Based on this information, we only have one IP network that can be assigned. That one network could Continue reading
The latest release of Cisco Nexus 1000V for vSphere can handle twice as many vSphere hosts as the previous one (250 instead of 128). Cisco probably did a lot of code polishing to improve Nexus 1000V scalability, but I’m positive most of the improvement comes from interesting architectural changes.
Read more ...
The narrow stairway at 463 (and a half) Bryant Street was my first impression of working at Cumulus Networks. Victoria opened the door, and I said, “Wow, this door is tiny and those stairs- what is this, a speakeasy?” I got the sly, dry smile that I have come to see as indicative of Victoria and was escorted inside to the conference room of what looked like an empty apartment turned into an office. There, I met Kathleen and we chatted for half an hour. It was one of the most informal, comfortable, genuine experiences I’d ever had in a job search.
“Do you think you can commit to working at Cumulus Networks a few months, understanding it’s sort of up in the air right now, the future of this office, etc.?”
“Yeah, I think so. I mean, unless I become like, a famous author over night, or something. Which probably isn’t going to happen.”
Victoria glanced at my resume. “It says here that you published a book.”
“Two, actually. But you know… that’s how I Continue reading
Vendors keep telling me that every business is different and customer have different needs. We all buy the same products from the same companies, use the same deployment methodologies and best practices, have the same problems and deliver the same results to the business. You aren't a precious snowflake.
The post Rant: You Are Not A Precious Snowflake. IT Infrastructure Is The Same Everywhere. appeared first on EtherealMind.
The pilot episode of Software Gone Wild podcast featuring Snabb Switch created plenty of additional queries (and thousands of downloads) – it was obviously time for another deep dive episode discussing the intricate innards of this interesting virtual switch.
During the deep dive Luke Gorrie, the mastermind behind the Snabb Switch, answered a long list of questions, including:
Read more ...In my last post, we covered setting up the basic install of the Chef Server, the Chef client, and a test node that we bootstrapped with Chef. Now let’s talk about some of the basics and hopefully by the end of this post we’ll get to see Chef in action! Let’s start off by talking about some of the basic constructs with Chef…
Cookbooks
Cookbooks can be seen as the fundamental configuration item in Chef. Cookbooks are used to configure a specific item. for instance, you might have a cookbook that’s called ‘mysql’ that’s used to install and configure a MySQL server on a host. There might be another cookbook called ‘httpd’ that installs and configures the Apache web server on a host. Cookbooks are created on the Chef client and then uploaded and stored on the Chef server. As we’ll see going forward, we don’t actually spend much time working directly on the Chef server. Rather, we work on the Chef client and then upload our work to the server for consumption by Chef nodes.
Recipes
Recipes are the main building block of cookbooks. Cookbooks can contain the Continue reading
Monitor features in Cisco devices are able to show data flows but Cisco IOS lacks the option to export data on the fly. I wrote tiny GNU/Linux shell script to solve this restriction.
That is something like ASA capture (https://supportforums.cisco.com/document/69281/asa-using-packet-capture-troubleshoot-asa-firewall-configuration-and-scenarios) via HTTP/HTTPS.
I tested script on:
Router(config)#uname -a
IOSv Router IOS 15.4 Cisco IOS Software, vios Software (vios-ADVENTERPRISEK9-M), Experimental Version 15.4(20131213:232637) [lucylee-ca_pi23 137]
Copyright (c) 1986-2013 by Cisco Systems, Inc.
Compiled Mon 16-Dec-13 19:50 by lucylee Unknown Unknown IOS
1. Create user and add privilege level 15 (root)
username user secret userpass
username user privilege 15
2. Start HTTP server, authentication style and optional (set max connection to 16 (default 5))
For security reasons you should set HTTP/HTTPS authorization with ACL and instead of HTTP use HTTPS server.
ip http server
ip http authentication local
ip http max-connections 16
3. Configure Monitor settings
Below I created a circular buffer called MY_BUFFER. Linear buffer is limited that means, if buffer is full IOS will stop capture. In circular buffer "old" data will be rewritten when buffer is full.
monitor capture buffer MY_BUFFER size 1024 max-size 9500 circular
Next step is to create a capture point. I created the Continue reading
It’s long been assumed that Spammers use a technique called IP squatting to get around IP reputation lists and to make it harder to find the real source of the spammers. In this blog we’ll take a closer look at Spam operations and their techniques.
IP Squatting
We’ve all read the reports about IPv4 running out of free address space and while that is certainly true there’s still a lot of address space that has been allocated but is not actually routed on the Internet today. A significant portion of that space are prefixes that were allocated a long time ago and folks are no longer using these allocations, forgot about it or have other reasons to not use their IP address space on the Internet. IP squatters look for space that hasn’t been routed for a while and will claim ownership of the space. This can then be used for things such as Spamming. There is vast range address space that is not currently announced on the Internet and it is not uncommon for IP squatters to cycle through this space using one or more prefixes at a time for a brief period.
Below we’ll expose two actual Spam Continue reading
