That Ole Familiar “Network” Command
A basic concept, but one that is consistently the cause of confusion even in the most learned technical circles within Cisco networking, is the specific role that the “network” command plays in various routing protocols. The reason for this confusion? The use of the word “network” itself. Let’s explain. The Problem Let’s say you had a shiny new Cisco router, and that router had 4 networks you wished to advertise (I used loopbacks for simplicity):The Dangers of Fanboyism
In the short amount of time since I tripped and fell into this industry, one thing is clear - fanboyism (Is that a word? It is now.) is EVERYWHERE. Those that love Cisco, really love Cisco. Those that love Juniper, really hate Cisco. It’s hard to start working in this industry, especially in a relatively single-vendor environment, and not acquire a strong affinity to one side of the other. Not to mention the fact that big companies like Cisco have huge, widely used and respected certification programs, so it’s easy for an engineer to take Cisco’s word as the word of god.The Importance of Effective Communication at Work
There are many different personality traits found in individuals in our industry. One trait that I’ve found dominant in technical roles is that of introversion. This trait is one that often manifests itself by creating challenges with verbal communications. Depending on an individual’s role, or desired role, this can prevent a technology rockstar from reaching […]
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The post The Importance of Effective Communication at Work appeared first on Packet Pushers Podcast and was written by Paul Stewart.
Nexus 5500 ASIC to port mapping
While assigning ports on a Cisco Nexus 5500 switch, it is a good practice to span out ports that belong to separate ASICs on board to uplink to upstream or downstream devices. For e.g. while connecting a 5500 to say a UCS FI, it is good practice to select 2 ports from one ASIC bay and 2 from another ASIC bay. The way you find out ASIC to port mapping is with the following CLI command : 'show hardware internal carmel asic <0-13>' where 0-13 are the ASIC numbers.
Here, Ports 9-16 are mapped to ASIC 1. On Nexus 5500 switches, 8 ports are mapped to each ASIC.
HP Moonshot
Despite my humble beginnings as a network engineer, I’m almost always including servers/virtualization/storage in my day-to-day work. If you’re not into building servers from scratch (not a bad venture) then the leaders in the server space might be a good fit for you - most are doing some pretty interesting things in the battle for the top spot in this space. Most folks would agree that HP is still the number one leader, even if only considering pure volume (I see c7000 chassis EVERYWHERE).HP Moonshot
Despite my humble beginnings as a network engineer, I’m almost always including servers/virtualization/storage in my day-to-day work. If you’re not into building servers from scratch (not a bad venture) then the leaders in the server space might be a good fit for you - most are doing some pretty interesting things in the battle for the top spot in this space. Most folks would agree that HP is still the number one leader, even if only considering pure volume (I see c7000 chassis EVERYWHERE).Crossbow on Big F#@!ing Webtone Switch
Back in the days of SUN Microsystem, Scott McNealy asked us to build a big F#@!ing Webtone Switch. At that time, the underlying pieces weren’t there but over last few years the possibilities have opened up. We now have the switch chips from Broadcom and Intel that switch at 1.2Tbps in H/W. From a OS view, 1.2 Tbps of switching at 300ns latency is great but the more amazing thing is PCIe as a control plane which allows 20-40Gbps of control plane B/W where you can change switch registers, L2/L3-tables, TCAMs, etc at nano-second rates.
So after more than three years of work and million lines of C code, the Pluribus Network’s engineering team has the switch chip under Crossbow control. For people who are not sure what I am talking about, in 2005 project Crossbow invented virtual switching inside a server hypervisor and introduced hardware based Virtual NICs and dynamic polling to get 40Gbps of bandwidth through a server OS. The details were published in “Crossbow: From Hardware Virtualized NICs to Virtualized Networks” in ACM Sigcomm VISA 09.
In the goal to benefit from merchent silicon ecosystem and orchestrate the entire infrastructure using Open source OS Continue reading
Show 155 – Integrating OTV, FabricPath & LISP – Sponsored
At Cisco Live 2013 in Orlando, Packet Pushers co-hosts Ethan Banks and Greg Ferro sat with Nexus 7000 champion Ron Fuller and network design expert Russ White to discuss how, when and why you might choose to deploy FabricPath, OTV, or LISP. In particular, we get into the specifics of what each protocol does, where […]
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The post Show 155 – Integrating OTV, FabricPath & LISP – Sponsored appeared first on Packet Pushers Podcast and was written by Ethan Banks.
IGP Metric Tweaks – Direction is Important
A while back I was responsible for setting up a group of switches and routers to serve as the internet distribution for a hospital, mainly the function of designing the IGP of choice to work given the hospital’s requirements and coordinating with the teardown of the old gear. The idea was to configure EIGRP so that one next-hop was preferred over another. We know this is possible through tweaking the various metrics for a given IGP, but in the process, I was reminded of something that’s quite important to think about when doing so.IGP Metric Tweaks – Direction is Important
A while back I was responsible for setting up a group of switches and routers to serve as the internet distribution for a hospital, mainly the function of designing the IGP of choice to work given the hospital’s requirements and coordinating with the teardown of the old gear. The idea was to configure EIGRP so that one next-hop was preferred over another. We know this is possible through tweaking the various metrics for a given IGP, but in the process, I was reminded of something that’s quite important to think about when doing so.IGP Metric Tweaks – Direction is Important
A while back I was responsible for setting up a group of switches and routers to serve as the internet distribution for a hospital, mainly the function of designing the IGP of choice to work given the hospital’s requirements and coordinating with the teardown of the old gear. The idea was to configure EIGRP so that one next-hop was preferred over another. We know this is possible through tweaking the various metrics for a given IGP, but in the process, I was reminded of something that’s quite important to think about when doing so.Healthy Paranoia Show 15: The Dudes of REN-ISAC
It’s the latest dudilicious episode of Healthy Paranoia! This time we’ll be covering the topic of information sharing and analysis centers (ISAC), specifically in the research and educational networking sector, aka REN-ISAC. Joining Mrs. Y on this adventure into the land of dudeness is Wes Young, REN-ISAC Principal Security Engineer and Architect (El Duderino), Keith […]
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The post Healthy Paranoia Show 15: The Dudes of REN-ISAC appeared first on Packet Pushers Podcast and was written by Mrs. Y.
Lessons Learned Writing a Custom Config Builder
A while back, I set about developing a modest configuration templating system for my employer. When I first joined the company, new network devices were being provisioned using configuration templates stored as Microsoft Word files, which, as you can imagine, was pretty painful. Each variable had to be identified and replaced by hand in a tedious and error-prone process. I wanted something better, but also cheap (or free) and simple. So I started building something.
To kick off my crazy project, I first decided to build a web application based on the Django Python framework (the same platform on which PacketLife.net runs). Django and similar frameworks handle most of the mundane tasks involved in writing a web application and allow for rapid prototyping. It also includes a built-in administration interface for creating and manipulating data independent of the front-end user interface. I spun up a modest internal VM running...
You got promoted, now what?
Leadership in most companies is not really something explicitly practiced. Generally, a few people who are naturally inclined kind of do their thing while the rest of the leadership ranks sort of ignore the finer points of people management. But why is that the case? And how do you avoid being one of those leaders […]
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The post You got promoted, now what? appeared first on Packet Pushers Podcast and was written by Michael Bushong.
Confusing The Familiar with The Superior
We all know the archetype of the fanboy (or fangirl of course, however I will forthwith use zealot as a gender-neutral term). They expound upon the superiority of their favorite… whatever, and lambaste the competing product or products, and will hear of nothing that would contradict their conclusions. The battle the zealots fight are well known: […]
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The post Confusing The Familiar with The Superior appeared first on Packet Pushers Podcast and was written by Tony Bourke.
PQ Show 30 – RPKI DNSEC and Internet Security with Ivan Pepelnjak
There are two proposals floating around that are trying to address BGP origination hijacks (aka Pakistan vs. YouTube): RPKI and DNSSEC-based system. Ivan Pepelnjak joins Greg Ferro to talk about what is means for Networking. This show was recorded in January 2013 and it’s been delayed publishing. Please accept my apologies. Show Links Opinionated background […]
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The post PQ Show 30 – RPKI DNSEC and Internet Security with Ivan Pepelnjak appeared first on Packet Pushers Podcast and was written by Greg Ferro.
Quality of Service (QoS) Congestion-Avoidance Notes
Congestion-avoidance tools are complementary to, and dependent upon, queuing algorithms. Queuing/scheduling algorithms manage the front of a queue, while congestion-avoidance mechanisms manage the tail of a queue.
Congestion-avoidance tools are designed for TCP traffic, because TCP has built-in flow-control mechanisms that operate by gradually increasing traffic flows until packet loss has occurred. Once packet loss has occurred, the transmission rate is reduced before slowly ramping up again. This means that if no mechanism is in place to control TCP, any particular flow has the ability to eat up all available bandwidth.
When there are no congestion-avoidance tools in place, and queues fill, tail drop occurs, which means all traffic is dropped.
In a constricted channel without congestion-avoidance tools, TCP connections eventually synchronize with each other – they ramp up together, lose packets together, and back off together. This is called global synchronization and basically results in “waves” of TCP traffic.
Congestion-avoidance tools has no real benefit or use for UDP traffic, because UDP traffic does not have any retry logic.
Random Early Detection (RED)
RED combats global synchronization by preemptively and randomly dropping packets before queues fill. Instead of waiting for the queues to fill, Continue reading
Calculating distances in meatspace
I'm working on an automated provisioning system for a very large VPN network. For each new VPN client, I need to select a headend site where VPN tunnels should land. The only data available is that which I can get from the sales and billing systems. This system offers me the zip code of the install site.Using the zip code of the install site, and the known zip codes of my various head-end sites, I'm able to select the destination for the primary and secondary VPN tunnels.
It's not perfect (physical location often has little to do with network path), but it's better than nothing. I haven't decided how to handle non-US sites yet.
I'm using a database of US zip codes found here, and a very dirty perl script. The script grabs the latitude and longitude of two zip codes from the database, and prints the mileage between them as calculated using the Haversine formula for great circle distance.
It runs like this:
Christophers-MacBook-Pro:scripts chris$ zipdistance.pl 95134 60614
1837 miles
Christophers-MacBook-Pro:scripts chris$
The script:
#!/opt/local/bin/perl
use GIS::Distance;
my $dbfile="/Users/chris/Downloads/zipcode.csv";
my $lat1,$lon1,$lat2,$lon2;
sub usage{
printf "Usage: $0 <zipcode> <zipcode>n";
exit;
}
if (@ARGV ! Continue reading
The value of Connectors in the workplace
In Malcolm Gladwell’s book The Tipping Point [affiliate link] the author identifies key roles that individuals play in spreading knowledge and ideas. Gladwell outlines two key roles, the maven and the connector. The maven is a person who accumulates subject matter expertise and is willing to distribute that knowledge on request. Think of a maven […]
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The post The value of Connectors in the workplace appeared first on Packet Pushers Podcast and was written by John Harrington.
CCIE Rack for Sale
I am selling my rack as I need to make some space and I am now using CCIE Rack Rentals all the time which I find are so much more convenient. Only for UK as it is collection only, but if you are in the market for a CCIE Rack based on the INE topology […]
The post CCIE Rack for Sale appeared first on Roger Perkin - Networking Articles.