The second part about OVT in a previous post.
As promised, here are the slides from the presentation about OLV.
Feel free to download the slides Data-Center_Interconnect_Architecture_and_Solutions. (5mb)
Archive for the ‘General info’ Category
OTV Part II
February 26, 2010Overlay Transport Virtualization (OTV)
February 22, 2010I am currently attending a 2-day Cisco PVT seminar for Service Providers, where the Cisco boys are sharing some of the new and upcoming technologies and hardware on the roadmap from 2010 onwards.
Cisco Systems are where they are today because of their groundbreaking innovation.
After seeing some of the specifics and configuration, OTV really seems impressive.
What is OTV (Overlay Transport Virtualization)?
Working out Bc values quickly
February 9, 2010I was asked today how to calculate the Bc values. The known formulas always add confusion. So the aim of this article is not to add more confusion, but offer an easy alternate way to calculate the Bc values used with shaping.
First lets review some basic shaping definitions.
CIR (Committed Information Rate)
- Dictates the output rate one aims to average per second on the circuit/interface.
- Book formula : CIR = Bc / (Tc/1000)
Tc (Time-Interval)
- It is the time in milliseconds into which a second is divided for transmission intervals.
- The Tc can’t be adjusted directly, but it can be changed by setting the Bc to a specific value..
- The maximum value of Tc is 125ms (8 intervals per second) and the minimum value is 10ms (100 intervals per second).
- Actually 8ms (125 intervals per second) on distributed platforms. On distributed platforms, the Tc must be defined in 4-ms increments. The nearest multiple of 4 ms within the 10-ms target is 8 ms.
- Book formula : Tc = (Bc / CIR) x 1000
Bc (Committed Burst Rate)
- Bc is the number of committed bits allowed to be sent per interval (Tc) to conform with the target-rate (CIR) per second.
- If Bc worth of bits are sent every interval in a second, the output rate is the CIR.
- Book formula : Bc = CIR x (Tc/1000)
Configuration Lock
February 5, 2010Ever busy with a scheduled change, and the configuration all of a sudden differs from what you configured five minutes ago?
Normal IOS (not XR) behaviour allows multiple users to make instant changes to the running configuration. Occasionally two users make changes to the same config portion at the same time. One overwriting the others. ONLY the last commands entered will take effect.
The Configuration Lock feature allows a one to have exclusive change access to the Cisco IOS running configuration, preventing multiple users from making concurrent configuration changes.
There are two modes:
- Auto
- Manual
Getting your router to Tweet
January 20, 2010Ok, so an earlier post sharing a really neat geek trick is awesome, but how the hell does one go about configuring a router to tweet something? (if you not a programmer)
To do it, you would need the following:
- IOS image that supports EEM.
- A twitter account.
- A base64 encoded representation of you twitter account’s
- Bruno’s twitter script. Download tweet-policy.tcl here.
- The IP address of your nearest twitter server. (nslookup or dig will help you there)
The IOS obviously must support EEM.
Then once you have your twitter account, you need to encode your twitter account’s username:password to a base64 encoded representation. Could be done using this website. Example:
twitter-username:tweet-password
gives you
dHdpdHRlci11c2VybmFtZTp0d2VldC1wYXNzd29yZA==
Tweeting Bits
January 14, 2010
Routing-Bits is now Tweeting-Bits too.
Yes I know I should have done this ages ago 
But better late than never.
Feel free to visit twitter.com/routingbits
Route Selection with equal AD’s
January 7, 2010I had a interesting question from a friend today.
Assume the following scenario:
Im going to exclude any MPLS connectivity, as it is not relevant.
The PE (Router1) connects the CE (Router3) with two links, one serial and one wireless.
This particular ISP runs mostly static routes to client sites (within the VRF’s) or alternatively eBGP.
On a wireless link it is always good practise to run BGP to detect when connectivity with the remote end is lost in the underlying Layer2 network. (Preventing a blackhole)
Regarding routing on the Serial Link, there as a default route out from Router 3 and a static route to 10.33.33.0/24 on Router1 pointing to Router3.
The client wants to load-balance traffic across both links. And the Admin Distance of the static route was set to 20 to match eBGP. (this is the scenario)
So the question : Why does Router1 not install both routes (the eBGP route and the Static), both with an prefix-length of /24, a Admin Distance of 20, and metric of 0 into the RIB??
RIB Route-Selection
January 7, 2010Inspired by the flow chart that Mr Richard Bannister did for the BGP route path selection, I did one for conventional route-selection in the RIB.
HexBinDec Conversion
November 10, 2009I often see guys still using windows calculator to do Hex 2 Binary 2 Decimal conversions for Port numbers, Protocol numbers, DSCP values etc…
I have been using a small utility for years and have not yet come across a better one.
It was written by Live Bat Programming Group, I can’t find an official website only an email address : dagus2@geocities.com (not sure if it is still valid).
It is called HEXBINDEC (descriptive I know):
Searching for something?
November 9, 2009Everybody knows how to use the include|begin|exclude search operators (I hope so at least), but you can also search through config with the “/” operator. You can use this with almost any SHOW command that is more than one page long. Although similar to linux and useful it is only half as good.
I use this mostly when I want to see the configuration following a specific search string bound to show up multiple times from the SHOW command.
Example: Show the running-config, and one the first page break, hit the forward slash “/”. Now enter the string you looking for:
Read the rest of this entry ?
CPU and Memory Thresholding
November 2, 2009It is never nice when devices on a network go belly-up, but to know why or what happened right before they went belly-up, is crucial.
By enabling CPU and Memory thresholding, you can be sure to get those vital notifications when it happen allowing you to respond a lot quicker.
When a router is overloaded by processes, the amount of available memory might fall to levels insufficient for it to issue critical notifications, so the first step is to reserve some memory:
memory reserve critical {kilobytes}
Cisco IOS v15.0
October 21, 2009Cisco finally took the long awaited leap, and released a new Major Release. The latest Cisco IOS version was 12.4 until Cisco released IOS version 15.0.
Version 15.0? Surely that is a typo a mistake?
According to a forum or two, rumors is that Cisco avoided using 13 and 14 because 13 is considered unlucky in the Western Culture and 14 is also considered unlucky in the Asian culture !!
And I thought believing in superstition was bad luck! LOL
BFD – Bidirectional Forwarding Detection
October 20, 2009What is one pain-in-the-butt thing with wireless links connected to a Ethernet port on a Cisco router?
You don’t know when the wireless link goes down?
Since Ethernet technology does not provide for end-to-end connectivity checks, like ATM OAM F5, Frame-Relay EEK, or PPP LCP Keepalive, you need a similar method to know when the wireless link or the remote site is unreachable.
There are varies workarounds, eg using IP SLA monitor, or using BGP with reduced timers. A better solution is to use Bidirectional Forwarding Detection (BFD), to quickly identify the failing wireless VLANs and route your retraffic quickly and efficiently.
Cisco Data Centre Design and Deploy Workshop
October 16, 2009
.
I attended the Cisco Data Centre workshop the past two days at Monte Casino. With a huge attendance and both local and international speakers, one thing is for sure, the focus of technology and cabling around Data Centres are evolving and Cisco is leading the way as usual with Data Centre 3.0.
Key concepts discussed:
- Cabling Reduction
- No STP
- Unify, Simplify, Amplify
- Virtualization
- Unified Fabric Advantages
- Cloud Computing
- Unified Computing
Some of the biggest issues with data centres today, besides hitting scalability constraints, are the excess cabling, the power required per-port, the overall cost and unwanted complexity. According to Cisco by redesigning the Data Centre architecture from the ground (the cabling) up, utilizing 10 Gigabyte cabling options, doing ‘away’ with Spanning-tree in order to utilize ALL uplinks simultaneously, using Top-of-Rack fabric extenders, Middle-of-Row aggregation points, and with the power of Cisco’s UCS implementation, you will be enabled to streamline the layout, cost, power-demands, sustainability and scalability.
Obviously it wont be a Cisco event if there we no hardware talk, err I mean sales-talk. The guests of the conference were the Cisco Nexus Range of Data Centre Switches (the Nexus 1000V Switch, Nexus 2000 Series Fabric Extenders and Nexus 5000 and 7000 Series Switches) and lastly UCS (Unified Computing System).
Here are some of the links with more info:
IOS upgrade tip
October 11, 2009So it is sunday morning, the change window just kicked in, you copied the new IOS image to the router, used the ‘boot system’ command as per my previous post, you save your config and reload. All looking good for an early night, but when the router reloads you get a bunch of errors during bootup along the lines of:
% Invalid input detected at '^' marker.
% Incomplete command.
Oh no, you didn’t do you homework, did you check for command differences between the IOS versions? Did you test the current config on the new IOS in a lab prior to the upgrade (yes not always possible), do you have a config backup?
If you don’t have a full config backup you have BIGGER problems. If you remove the first ‘boot system’ command to boot of the working IOS, and write your config, usually all commands that gave errors during that boot-up, will now be LOST since you saved the config and overwrote the startup-config.
So what now?
Appose to freaking out and start dancing like a banshee doing some tribal dance, do the following. ‘Rename’ the NEWLY installed IOS image in Flash, the image specified in the first ‘boot system’ command to something else, and ‘Reload’ WITHOUT SAVING the config. When the router reboots it will attempt to locate the first specified boot system image, but because you renamed it, it can not be loaded. The router will then attempt to boot off the second specified boot system image, the old working IOS image. And happiness is restored.
