Category Archives for "Routing-Bits"

Handbook Updates

As many might have noticed, the Routing-bits Handbook updates have been sparse, and activity on the Routing-Bits blog even more so. A variety of contributors have led to this stemming from piracy, work, life, family, and relocation. With this I find myself at a cross-roads looking at the future the Routing-Bits website and the RB […]

Cisco VIRL goes public

It’s been a few years since the first whispers started leaking out about Cisco building an in-house software emulation platform. A Dynamips/GNS-like program that natively caters for the needs of Cisco students and engineers in the field has been a hot topic for a long time. Early last year Cisco made official mention that they […]

Routing-Bits SP Update

    The next installment of the SP handbook is now available. It includes two new chapters and an extra appendix. Please check your email for instructions. Contact me if your email address has changed.Filed under: CCIE SP

Troubleshooting MAC-Flushes on NX-OS

An interesting client problem in one of our multi-tenant data centers came to my attention the other day. A delay sensitive client noticed a slight increase in latency (20 ms) at very intermittent intervals from his servers in our data center to specific off-net destinations. The increase in latency was localized to the pair of Nexus […]

Detecting Layer2 Loops

We all too familiar with the devastating impact a talented layer 2 loops could have on a data center lacking sufficient controls and processes being in place. If you are using Cisco Nexus switches in your data center, you would be happy to know that NX-OS offers an interesting new tool you should add to […]

FEX Architectures

Here is an old post I never finished. With the benefits of the Nexus 2000 and the FEX architecture (a earlier post), scalability, simplified management, flexibility, Cisco extended its use further into the servers all the way up to the virtual hosts.This allows much greater control and flexibility. After all network guys should look after […]

Get-Console Review on the iPad

I have used my iPad to console onto Cisco routers and switches for about 2 years now. I started using the Flex-Serial cable on my jailbroken iPad and iPhone, with the iSSH app and a ported version of Minicom (earlier blog post).  Amidst some minor bugs and irritations this worked well and was considerably more […]

The Fabric ERA

“Fabric” is a loosely used term, which today creates more confusion instead of offering direction. What exactly is a Fabric ? What is a Switch Fabric? Greg Ferro did a post here explaining how Ethernet helped the layer 2 switch fabric evolve. Sadly the use of switch fabric did not stop there. And this is […]

What is a Fabric Extender

In this post I would like to cover the base of what is needed to know about the Cisco Fabric Extender that ships today as the Nexus 2000 series hardware. The Modular Switch The concept is easy to understand referencing existing knowledge. Everybody is familiar with the distributed switch architecture commonly called a modular switch: […]

N5K Stuck in Boot Mode

Another trivial post. The upcoming posts following this one will take a more in-depth look at the Nexus technologies. So you do an non-ISSU NX-OS upgrade on a Nexus 5000 switch and something goes wrong. After reload you get the following prompt: The switch did not successfully boot from the images it was suppose to. […]

Load-Sharing across ASICs

Port-channels have become an acceptable solution in data centers to both mitigate STP footprints and extend physical interface limits. One of the biggest drawbacks with port-channels is the single point of failure. Scenario 1- Failure of an ASIC on one switch, which could potentially bring the port-channel down, if all member interfaces were connected on […]

Nexus Accounting Log

Perhaps another trivial post, but if you don’t know about it, you might find it extremely useful. Cisco NX-OS has an on-device log file of the exec level configuration commands entered successfully. Obviously similar informational can be obtained from the TACACS logs, but there is a certain benefit in having directly on CLI. The command […]

Nexus load intervals

This is a interesting but a trivial post. Everybody know about the interface command “load-interval” that changes the time period over which the interface packet-rate and throughput statistics are averaged. I discovered an addition to this command on the Nexus the other day while poking around. NX-OS allows multiple counter intervals to be configured on […]

Cisco Nexus 7000 upgrade to 8Gb

When upgrading a Nexus 7000 to NX-OS version 5.2 (using more than 1 VDC) or to NX-OS v6+, Cisco claims the need to upgrade the system memory to 8Gb. Note I have run on v5.2 using only 4Gb per SUP using 2 VDCs and it has worked just fine, but I should mention that the […]

Omnigraffle Stencil for Cisco Nexus

I am a MAC user and I have been looking but could not find a OmniGraffle Stencil with the Cisco Nexus icons, so I ended making one. I have also submitted the stencil to Feel free to download it and from Graffletopia or Mediashare:Cisco Nexus Hardware.gstencil.zipFiled under: General info

Cisco and their inconsistencies

Cisco is known for the inconsistencies between platforms and different IOS versions. I came across another that was rather annoying. Now between linecards. Trying to configuring the following standard sub-interface Ethernet AToM tunnel on a Cisco 7606 with a ES+ linecard: Yields the following misleading error… This is enough to annoy you for some time. […]

BGP between Cisco Nexus and Fortigate

It is not uncommon to find that different vendors have slightly different implementations when it comes to standards technologies that should work seamless. I recently came across a BGP capability negotiation problem between a Nexus 7000 and a client Fortigate. Today’s post is not teaching about any new technologies, but instead showing the troubleshooting methodology […]

Cisco Nexus User Roles using TacPlus

I previously wrote a post about the Nexus Roles and how they integrate with a TACACS server. Cisco Documentation shows the following format to issue multiple roles from a TACACS/RADIUS server.: We are using Shrubbery TACPLUS, instead of the Cisco ACS software. Last week I noticed that only one role was assigned when multiples should […]

Low Memory Handling

Memory problems on routers is nothing new. It is generally less of a problem in current day, but is still seen from time to time. BGP is capable of handling large amount of routes and in comparison to other routing protocols, BGP can be a big memory hog. BGP peering devices, especially full internet peering […]