Cisco onePK Screencast
As a follow-on to my previous article on onePK — Cisco onePK: Now I Get It — I recorded a screencast in which I talk about what a onePK-enabled network is capable of. I also demonstrate two applications which make use of onePK to gather telemetry from the network and also program the network. MTU Checker - Verifies that when the MTU of an interface is changed on the CLI, that the adjoining interface MTU matches Routing For Dollars - Programs the forwarding table of the routers in the network based on the cost — in terms of dollars — of the various links in the network Please leave a comment below with any questions or feedback.PQ Show 29 – How To Prepare for the CCDE
At Cisco Live US 2013 in Orlando, Packet Pushers co-host Ethan Banks was joined by CCDE program manager Elaine Lopes, CiscoPress author Russ White who was closely involved with the CCDE program creation, quad-CCIE & CCDE Scott Morris, and CCIE & CCDE Jeremy Filliben who instructs a CCDE bootcamp. We discuss (what else) how to […]
Author information
The post PQ Show 29 – How To Prepare for the CCDE appeared first on Packet Pushers Podcast and was written by Ethan Banks.
Quality of Service (QoS) Congestion Management Notes
Of all the tools within the QoS toolset, congestion management tools, also known as queuing tools, provide the biggest impact on application service levels. Whenever packets enter a device faster than can exit it, congestion exists and this is where queuing tools come into play. Queuing tools are only engaged when congestion exists, otherwise packets are sent as soon as they arrive. When congestion does exist, packets must be buffered, or queued, to mitigate dropping.
Packet markings, or lack thereof, affect queuing policies, so queuing policies are complementary and have a dependence on classification and marking policies.
Scheduling vs. Queuing
These two terms are often incorrectly used interchangeably – they are two different things. Scheduling determines how a frame or packet exits a device. Whenever packets enter a device faster than they can exit it, as is the case with speed mismatches (ex. Gigabit Ethernet traffic heading to a WAN interface), congestion can occur. Devices have buffers that allow the temporary storing and subsequent scheduling of these backed-up packets, and this process is called queuing.
Inbound traffic > Queuing (During congestion) > Scheduling > Outbound traffic
- Queuing – orders packets in linked output buffers. Only Continue reading
Quality of Service (QoS) Classification and Marking Notes
The first part of building a QoS policy is to identify the traffic that you need to treat preferentially (give better priority), or differentially. This is accomplished via classification and marking.
- Classification – sorts packets into different traffic types that policies can then be applied to.
- Marking (or re-marking) – establishes a trust boundary on which scheduling tools later utilize. The edge of the network where markings are either accepted or rejected is known as the trust-boundary.
- Classifier tools – Inspect one or more fields in a packet to identify the type of traffic that is being carried. After being identified, it is passed to the appropriate mechanism to handle that type of traffic class.
- Marking tools – actually write a field within the packet (or frame, cell, label) to preserve the classification decision. By marking traffic at a trust boundary, subsequent nodes do not have to perform the same in-depth analysis to determine how to treat the packet.
Classification Tools
These tools can examine a number of criteria within layers 1, 2, 3, 4, and 7.
- L1 – Physical interface, subinterface, PVC, port
- L2 – MAC, 802.1Q/p CoS, VLAN, MPLS EXP, ATM Cell Continue reading
Checksum Verification
Occasionally I have to install software that is no longer available for download via the official channels. This is due to us having pretty strict standards on which IOS versions are stable and suitable for use via a bug scrub process that Cisco are party to.
I could speak to our Cisco SE and ask for the image to be provided, but it’s simpler and quicker to find a similar piece of kit on the network and FTP/SCP the image across.
I did this today, and then realised that I couldn’t rely on CCO to give me the MD5 sum for the image. A quick google tells me that I can perform a checksum on the switch using this command:
verify /md5 <file-location>:<file-name>
Location choices are:
bs: File to be verified
cns: File to be verified
flash: File to be verified
ftp: File to be verified
http: File to be verified
https: File to be verified
null: File to be verified
nvram: File to be verified
rcp: File to be verified
scp: File to be verified
system: File to be verified
tar: File to be verified
tftp: File to be verified
tmpsys: File to be verified
xmodem: File to be Continue reading
Change your vocabulary, change your career
When people look at their careers, the focus pretty naturally falls to skills acquisition. Almost everyone believes that their future hinges on learning some skill or mastering some talent. Maybe you want to know more about business or strategy. Perhaps you think you need to read leadership books or find Harvard Business Review articles on […]
Author information
The post Change your vocabulary, change your career appeared first on Packet Pushers Podcast and was written by Michael Bushong.
Invest in great tools for your engineers
Can you remember your last newly hired engineer, all shiny and happy and new? Can you also remember the look on their face when they received their corporate craptop? Or maybe they received a decent laptop, but it came in a ten dollar laptop bag. The tech industry spends a lot of time and effort […]
Author information
The post Invest in great tools for your engineers appeared first on Packet Pushers Podcast and was written by John Harrington.
Don’t Alienate Your Co-Workers With Your Passion
We geeks love our tech. Really love it. I mean…really, really get down deep into a technology, decide it’s the best thing ever, and then wave the flag around high. Make the wallpaper. Wear the t-shirt. Evangelize the ignorant. Shout down the naysayers. Mock the competitors. Fan the flames of rivalry. Linux vs. Microsoft. Mac […]
Author information
The post Don’t Alienate Your Co-Workers With Your Passion appeared first on Packet Pushers Podcast and was written by Ethan Banks.
CDN activity and what it means for network monitoring
One of the more useful ways to find out what is happening in the real world of network monitoring and troubleshooting is to have a look through some of the many on line forums that exist. Spiceworks Community and SolarWinds Thwack are examples but there are many more. Here you can spot trends as to […]
Author information
eFSU on VSS (WS-6513, Sup2T)
I performed an eFSU (enhanced Fast Software Upgrade) of a pair of Cisco WS-6513-E switches in VSS. eFSU is the closest one can get to a true ISSU (in service software upgrade) of a VSS chassis. The entire process took 25 minutes. It is slower than a conventional FSU that involves changing the boot variables on the switch to point to the new software image file and then reloading the switches. This will cause a complete outage irrespective of whether devices are single or dual attached to the VSS. With the eFSU, we lost a single ping in the complete process from a workstation that was connected to an upstream 4500 switch that was dual homed to the VSS chassis. However, for devices that were single attached, there was a considerable outage (60-180 seconds).
I'll go over the process and hopefully this post should familiarize other network engineers who want to attempt an eFSU but haven't done it before. I've capture screenshots of the upgrade process, so we can look at some of the interesting logs on the switches.
Current IOS: 15.1(1)SY
New IOS: 15.1(1)SY1
Cisco's documentation is very precise and straight forward and can be found here.
Visibility, Debugging and Network Virtualization (Part 1)
[This post was written by Martin Casado and Amar Padmanahban, with helpful input from Scott Lowe, Bruce Davie, and T. Sridhar]
This is the first in a multi-part discussion on visibility and debugging in networks that provide network virtualization, and specifically in the case where virtualization is implemented using edge overlays.
In this post, we’re primarily going to cover some background, including current challenges to visibility and debugging in virtual data centers, and how the abstractions provided by virtual networking provide a foundation for addressing them.
The macro point is that much of the difficulty in visibility and troubleshooting in today’s environments is due to the lack of consistent abstractions that both provide an aggregate view of distributed state and hide unnecessary complexity. And that network virtualization not only provides virtual abstractions that can be used to directly address many of the most pressing issues, but also provides a global view that can greatly aid in troubleshooting and debugging the physical network as well.
A Messy State of Affairs
While it’s common to blame server virtualization for complicating network visibility and troubleshooting, this isn’t entirely accurate. It is quite possible to build a static virtual datacenter and, assuming the vSwitch Continue reading
The Value of Certifications
I hope to clear the air on what a vendor certificate (or any certificate, such as a degree/diploma/etc) is, and is not. Too many times have I heard/seen people place too little or too much stock in the single piece of paper. What a certificate is A certificate, simply put, is proof that on a […]
Author information
The post The Value of Certifications appeared first on Packet Pushers Podcast and was written by Ken Matlock.
Cisco onePK: Now I Get It
I had an opportunity recently to sit in a Cisco onePK lab and it opened my eyes to exactly what Cisco is doing with onePK, why it’s going to be so important as Software Defined Networking (SDN) continues to gain traction, and why onePK is different than what anyone else is doing in the industry.
onePK is a key element within Cisco’s announced Open Network Environment SDN strategy. onePK is an easy-to-use toolkit for development, automation, rapid service creation and more. It enables you to access the valuable data inside your network via easy-to-use APIs.
Source: www.cisco.com/go/onepk
Since having my own eyes opened, I’ve been pondering how to explain my new found understanding in a way that others will grasp. In particular to business decision makers (BDMs) and technical decision makers (TDMs). I’m really, really, struggling to come up with a good analogy for BDMs. I’m still working on that one. Surprisingly, I’m also struggling to come up with a sound analogy that will work with the majority of TDMs that I know. Maybe I shouldn’t be so surprised at that since all the TDMs I deal with are on the infrastructure side of things (networks, storage, Continue reading
Show 153 – Cisco Live 2013 Roundtable Discussion with Tech Field Day
At Cisco Live US 2013, we were able to get together a nice group of folks to share their opinions on the announcements we found most interesting. You’ll know some of them from Tech Field Day, an event Greg and I have been a part of several times. This show is good conversation with smart […]
Author information
The post Show 153 – Cisco Live 2013 Roundtable Discussion with Tech Field Day appeared first on Packet Pushers Podcast and was written by Ethan Banks.
Cisco onePK: Now I Get It
I had an opportunity recently to sit in a Cisco onePK lab and it opened my eyes to exactly what Cisco is doing with onePK, why it's going to be so important as Software Defined Networking (SDN) continues to gain traction, and why onePK is different than what anyone else is doing in the industry.
onePK is a key element within Cisco's announced Open Network Environment SDN strategy. onePK is an easy-to-use toolkit for development, automation, rapid service creation and more. It enables you to access the valuable data inside your network via easy-to-use APIs.
Source: www.cisco.com/go/onepk
Since having my own eyes opened, I've been pondering how to explain my new found understanding in a way that others will grasp. In particular to business decision makers (BDMs) and technical decision makers (TDMs). I'm really, really, struggling to come up with a good analogy for BDMs. I'm still working on that one. Surprisingly, I'm also struggling to come up with a sound analogy that will work with the majority of TDMs that I know. Maybe I shouldn't be so surprised at that since all the TDMs I deal with are on the infrastructure side of things (networks, storage, Continue reading
Your Career – Enemies Within and Without
In the mood for some self analysis and reflection around your career and your employer? Good. I’ve strong feelings about employment in general and even stronger ones around balancing it with your personal life (I wouldn’t dare say private any more) and making work work for you. I’m definitely in the work to live camp. […]
Author information
The post Your Career – Enemies Within and Without appeared first on Packet Pushers Podcast and was written by Steven Iveson.
Heatsink Upgrade
A little detour from the networking topics today to show off a little weekend tech project. I recently ran into some overheating problems with my home BYO PC. Core Temp was showing upwards of 70 degrees Celsius during normal operation, and under load, it would sometimes just shut down completely. Here’s the setup I had as of 2 days ago: The rear fan, which takes air in, was not working due to a short.Heatsink Upgrade
A little detour from the networking topics today to show off a little weekend tech project. I recently ran into some overheating problems with my home BYO PC. Core Temp was showing upwards of 70 degrees Celsius during normal operation, and under load, it would sometimes just shut down completely. Here’s the setup I had as of 2 days ago: The rear fan, which takes air in, was not working due to a short.Network Security and the N00b Meter
This morning I read an article in which the writer thought that wireless security was too inconvenient and difficult, so he simply disabled it, leaving his network wide open. He was tired of his complex password being too hard for guests to use and made the comparison that they didn’t have to use these kinds […]
Author information
The post Network Security and the N00b Meter appeared first on Packet Pushers Podcast and was written by Mrs. Y.
Optimizing and Protecting Spanning Tree – Lab Testing
Unfortunately the equipment I was using didn’t support PVST+ (Sup2Ts in 6503 Catalyst Switches), so I skipped testing UplinkFast and BackboneFast as these are incorporated in 802.1w (RSTP) and 802.1s (MSTP, which is basically an extension of RSTP).
BPDU Guard
For this test, SwitchD will be treated as a Rogue Switch being attached to the network. Initially, SwitchC’s port 2/1 is configured as an access port with only PortFast enabled.
- 1. Disconnect link between SwitchC and SwitchD
- 2. Configure SwitchC port 2/1 as an access port in VLAN 10 with PortFast enabled.
- 3. Configure SwitchD port 2/1 as an access port in VLAN 10. Configure the priority on VLAN 10 to be 0.
- 4. Reconnect link between SwitchC and SwitchD and check topology for VLAN 10. SwitchD should be the root for VLAN 10.
- 5. Disconnect link between SwitchC and SwitchD
- 6. Enable BPDU Guard on Switch C port 2/1
- 7. Reconnect link between SwitchC and SwitchD. SwitchC port 2/1 should move to an err-disable state. Verify with sh interfaces status err-disabled. Verify SwitchD is no longer the root for VLAN 10.
*Jul 5 22:02:06.023: %SPANTREE-2-BLOCK_BPDUGUARD: Received BPDU on port GigabitEthernet2/1 with BPDU Guard enabled. Disabling Continue reading