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Running Unbuntu as a Diskless system.

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Full Instructions from Unbuntu

Well the first question you might ask is why?

  1.  Allows you to boot a system to a second OS leaving the host hard drive untouched, this is similar to a duel boot but rather than having to set up duel boot on every device, you only need them all to have network boot enabled, and can manage the rest from a central server.
  2. Allows several hosts to boot from the same file system, very useful for some thing like “folding at home” where you might want to uses the resources of a users PC when they are away (out of hours) but do not want to have to install on to there profiles/OS. Changing the single file system updates every machine.
  3. You can build up mutiply images on the server, each streamlined for a specific job, and simply chose which one to boot to ad-hoc.

In my case I have used this for two purposes, first to run a computer cluster for disease modelling using a system called Condor, booting 16-20 users desktops to a single network image and using them to run models of disease spread for scientific papers.

And now more recently I have used the same principle for creating a GNS3 lab. I have several old laptops, as well as wife’s PC and even an old server. While at work I have access to servers and other lab equipment. I am not able to install Dynamips (GNS3’s back end), on to them all, and even if I could GNS3 runs far more stable on Linux than windows and I can’t guarantee other people will not uninstall or do any thing else that would stop it working.

The basic steps are to install Linux to a single machine, after which you copy this FS to your Server. (you need a server that supports PXE booting, TFTPD, NFS, and DHCP with PXE support)

And second set up your DHCP server to pass the name of the tftp serve along with the location on this server for a boot file.

Now there are more steps and the walk through above is a complete detailed process to get it up and running. If you have a few old boxes around you don’t know what to do with it fun to play with.  And will really help you learn the Linux FS.

DevilWAH

 

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I need to learn more C#

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Been playing around with it a lot, but come to the conclusion that I need to learn a bit more out of a book, than just using google and Microsoft sites. To be fair not done badly just a few areas I have been working on lately the code is a bit messy and I know there must be a better way to do it. So to help me on my way I have done two things.

Number one. Brought a Kindle, or to be more accurate my wife has got me one, just awaiting its arrival.

Number two. Getting hold of “Headfirst in to C#” and a few other C# books for it.

Hopefully by the end of this week I will have achieved the following in my application.

  1. Added controls to the output form for “Next config” and “Cancel”, Plus a button to copy to clipboard or download to file.
  2. Added the ability to create a single output from multiply lines in the entry form, and ability to chose a single line and out put only that config.
  3. After that I will be adding a header and footer section to the templates, that will all user to enter varibles aht are to be standard to all configs. Things like company information, user name, date, etc.

All simple stuff but just making sure it do it right now so when it comes to updating later it is all nice and clear. All about adding controls at run time at the moment and making sure its done in the most efficient way.

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ConfGen update.

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Spent quite a bit of time lately with this, the more I get in to C# the more impressed I become, I use to think that C# and .NET where only for people who couldn’t learn C++, but now I see the point. C++ is fun to learn, but it is very involved and I know I would be no where near as far along with this if I had decided to go down that route. OK C# requires the .NET framework to be installed on the client machine, but as for as developing goes it hit a nice sweet-spot, between the simplicity of VB, and the maze of C++. I would definitely suggest any one wanting to develop Window based applications to have a look.

As for ConfGen made a number of changes to the code to add some more functions, but still got lots more to do, see the ConfGen Page above for more details. This really is the middle application in terms of the long term goal. I also want to produce a tool that will build configs from scratch based on users specification, and a final implementation tool to deliver configuration to devices.

Also it looks like soon I should have a bit more time at work so CCNP study will be back in the picture. Thinking maybe to buy a Kindle and get the CCNP Foundation Guide as an Ebook, the hard back is just to heavy to lug around, so having it to hand on the Kindle for any spare time i get would be great.

Anyway back to some more coding now.

DevilWAH

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Continuing in to C# and Automation.

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So still not had much time to be studying CCNP, but have been getting my hands dirty on C# around the automation of generating configuration for cisco devices.

As mentioned before part of my job is change management which means a lot of repetitive configurations. In the past the tools I have written in VB and Excel have been limited to a single master config, what I decided was needed was a tool that could take a generic config written in notepad or other simple text editor and present the variables to the end user in a friendly form, for them to complete and generate the config.

Confgen

Screen shot of early version of Confgen

This is currently has a simple template loaded for changing the vlan and description of a port and enabling / disabling it. But the application is flexible to be able to take any length or complexly of config you can enter.

There are still lots of things to tidy up,

currently only the first row of variables entered can be parsed in to a complete script, I also want to eventually use a word template to give a professional output for the final script. And have a menu driven system that will look for files in a specified folder at start up and load them ready to be picked by the end user.

However its a start and the core of the application is working. I would say its still very much a Beta version, but am hoping over the coming weeks and months to develop it in to a much more compete tool. A few bugs to resolve and functions to add but I hope it gives people an idea of what i am looking achieveive.

I also have a stage 2 idea to add to this that will make it even mousefulull for new deployments to build up complex configurations, as well as these simple snipits.

If any one wants to try it out the zip file is below, simple extract to a folder and run, file >> open. to open the included example. (you will need .net version 3.5 framwork installed to run it)

Confgen

Please play around and let me know what you think.

Edit: added page to site to keep track of this tool and its development, see above.

DevilWAH

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OK back for another shout

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Well work still busy, and still struggling to find the time to study for my ROUTE exam. But that does not mean I have been doing nothing.

Work sent me on my ITIL Foundation course last week and please to say I passed, so thats one more string to the bow. I was suprised it was a lot more intresting that I thought, and while it still was in my view ‘common sence’. seeing it all togather with all the termonology, does mean I can now look back on some conversations I have had in the past and make some sence of them. For any one looking to get in to the managed service side of things, or wants a foot in the door for such company, it going to be a good cert to have.

The other thing that has been keeping me away from the CCNP is learning scripting and c#. I have already talked about writing some VB scripts to control Secure CRT. but of course to do this you need CRT installed on the PC in the first place. So taking it one step further I started looking at SecureCRT client pack, this is a instulation, that once installed on a PC, you can then call the functions when programing in any .net language, such as VB.net or C#.net This gives much more control over the application and gives the end user a much cleaner interface to use. However you still need to have the client pack installed and this costs money and the hassle of instulation.

So my next stop was Sharp SSH , this is a free SSH libuary with some simmler funcanality to the SecureCRT function pack (for what I want) and allows eaiser distribution of the final aplication.

So after a few steps, and lots of playing around, I now have the core understanding I need to start creating my vision. So as well as working on my CCNP, looking after my Daugher, and atempting to move house. Not forgetting the extra hours that come from managing at work. I am working on creating an application that will allow you to create a libruay of scripts you wish for CISCO IOS/CATOS devices. Including any pre / post checks you require and how to ack on there out comes, Plus allow you to define any varibles that will change between runs. Then allow you to feed in the varibles at run time (either manualy or via a bulk method), and carry out the work completely automated.

Really this is jsut a project for me to learn some more in depth scripting / programing, but as people who carry out mutiply changes, this can often be a repetive job, so I am hoping once complete I will end up with a tool that is very useful for my current postition.

So if you wondered where I was thats about sums it up. Life is great just very busy, and just waiting to get our house sorted, then I will be setting up a nice quiet area to study and getting stuck right back in to CCNP and getting back in to updating and adding to this blog.

night all

DevilWAH

PS. Oh and Miss Lilith is now walking, from bum shuffling to walking has taken less than 10 days, and not only is she walking but climbing to!! she is very proud to show how she can climb on to the couch, and thinks it is very funny to give Mum and Dad heart attacks by almost falling. But its a great time and wonderful watching her grow. being waved good bye to in the mornings, and greated with a huge smile and laughter when I get home, make life very special at the moment. 🙂

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VB again

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Well again its been a while since I posted, and once again I have been sidelined from CISCO studies.

A few weeks back I was asked to audit 1500 ports for a client, so thre was no way I was doing that by hand, I am a manger after all you know ;). But it was a great excuse to great a bit of scripting experience in scripting / programming.

Secure CRT has great scripting support and after a few hours playing around I had a script that can read from an excel spread sheet and carry out a list of checks and record the results.

1500 ports spread over 260 devices = 15 min, compared to the 20hr + I worked out it could have taken by hand including preparing the report.

But this lead me a bit further, what would be nice is a program that you could input any amount of code, where varibles where highlighted like. 


conf t
int ***port***
description ***des***
speed ****speed****

along with a spread sheet that contained columns containing the variables, and the program could loop through the rows implementing each line as it goes.

In my job there is the potential of having to implement the same config on multiply devices with different values (ie assign ports to vlans)

So for the last few weeks, VBA, VB script and C# have been taking up my life, its been great fun and while maybe not my CCNP still good skills to have as a network engineer to be able to automate things and increase throughput.

hope to be back soon with more updates…

On and other news…. Lilith was one at the weekend, happy birthday my beautiful little girl, you are and angel and very much loved by me and your mum 🙂 XX

DevilWAH

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CCNP SWITCH EXAM

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Well I was going through emails a few weeks back and came across an email for cisco with an exam voucher for the switch exam. (from back last year when the exam crashed on me). Checking it out the date was 17th march!!! (today).

With new job and baby, i havent had much time to study, as the lack of posts should tell you. But rather than wast the voucher i booked the exam and dusted of the books. After 2 weeks of sporic studying i sat the exam.

I think i might of actuly punched the air when i saw i passed at the end!!! And actuly with a half decent score.

But even better I now feel like i have the bug again, work has taken me in a slightly different direction. Still network but managment and not quite as hands on. Time to change that I and get CCNP done and dusted.

Hope that will also mean more posts as well. 🙂

Take care all

DevilWAH

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A bit of perl while I’ve been away (Always including some CISCO of course).

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Well no matter how many times I head back to post just lately I have never had the time. Studying been put on hold, house move on hold, and working falt out at the new job, but I have to say it has been fun.

Like I say not much studying done, but I have been playing with perl scripting latley. So rather than post nothing I thought I would share the results with you.

At work one of my teams jobs is to provision ports and reclaim ports on switchs. we basicaly write scritps during the day and then batch implement at night. So to make things a bit simpler, (and casue I was bored) I wrote a little web page using perl scripting as the back end.

Now I know I could use client side scripting to get a neater effect, and / or a stand alone program. But one thing about this was I wanted it as client friendly as possible, so decided to go for a web interface. And I have been meaning to learn a scripting language for ages so this seemed an good opportunity.

The web page is in two parts, one for provisioning ports and a second for reclaims, both can handle CATOS and IOS configs

They both still need some tidying up and I want to add some better functions to them soon, but Just so you don’t think i have disappeared here’s the link is you want to try them out. 🙂 (they link to each other)

Port provisioning script

The reason it is set out as it is, is that for my job servers are duel link to two switch, so for each script we are provisioning 3 or 5 ports per server mostly. Also the second switch is normally a mirror of the first, so by ticking the copy check box you only then need to fill in the interface on the second switch, the vlan, speed, duplex, ilo (integrate lights out for use when server crashes to remote reboot and get access to the bios) and sub-net information will be copied from the first switch. Port description as set to the name of the server configured.

I want to put some error checking in the webpage so users can’t skip filling in fields, and then expand to allow users to alter the number of switch / interfaces on the fly.

But for now it seems to work OK, and definitely speeds up or scripting tasks.

Let me know what you think 🙂 If you have any suggestions or would like to see the source code let me know. If you wold like a bit more in depth of what I did may be i can do a follow up artical at some point.

Cheers

DEVILWAH.

PS. little baby is doing great. 9 months old and I finaly understand what people mean when the say how life changing having a baby is! Miss Lilith as she is know in our house is laughing smiling and generaly making my life great. Can’t wait for the warm weather to take her out more 🙂

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Spanning Tree enhancements (Backbone Fast)

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Last time I look at the spanning tree enhancment I covered uplink fast, this is for detecting when a directly connected root port fails and switching over to a back up in the shortest time possible. But what happens if the link that fails is not directly connected. When a switch loses its link back to the root and needs to find an alternate path back. In the digram below switch B is blocking its port to Switch A to prevent loops.

The question is what happens if the link between Switch A and the Root fails? Well with out backbone fast the following sequince takes place.

When the link fails Switch A will no longer be receiving BPDU’s from the root, the direct link is down and the port on switch B is blocking so not forwarding BPDU’s.

Switch A will assume it is the new root and start to send BPDU’s towards Switch B declaring it is the root. However Switch B will see these are inferior BPDU’s to the on it has stored for the port connected to Switch A and ignore them.

This will continue to happen until the BPDU on the port times out, after which the port will go in to the listing and learning state before starting to forward. This is 20 seconds (max age timer) plus 2 x 15 seconds for the listing and learning stage. so a total of 50 seconds.

The idea behind Backbone fast is to cut this by 20 seconds by bypassing the max age timer. The idea is that if Switch B can confirm it still has a link back it’s current known root switch, then it can ignore the max age timer and start the listing and learning process on a port immidatly it receives a inferior BPDU.

Once backbone fast is enabled, when a switch receives a inferior BPDU on one of its ports, it will send a RLQ (root link query) packet out all it’s non designated ports including its root port (so all ports that lead back to the root). If it receives a RLQ response (these are sent from the bridge) then it knows it still has a link to root. It can then age out the port it is receiving the inferior BPDU’s on and start the listing learning stages. If it does not receive any responses then the switch has lost connectivity to the rest of the network and needs to start recomputing the whole STP.

Either way the max age time has been eliminated and 20 seconds have been shaved of the re convergence / fail over time.

Just like Uplink fast Backbone fast is configured on a switch level with the following command.

Switch(config)#spanning-tree backbonefast

and it needs to be configured on all switches on the network.

CISCO’s document HERE explains it in much more details and more examples.

DevilWAH

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CCNP ROUTE (Part 10 EIGRP Over NBMA)

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In what I think will be the last post on EIGRP (I will save redistribution between routing protocols for another time), I want to look at what is needed to insure EIGRP runs smoothly over NBMA (non broadcast multi access) networks such as Frame Relay.

As I have covered before EIGRP relies on multicast hello messages to form its neighbour relationships, but NBMA network by default do not forward any broadcast or multicast traffic. So this is the first issue with getting it up and running.

To achieve this you have two choices. First you could if you wished manually set up the neighbours. Going under the EIGRP AS process you can issues the command

router#(config-router)#neighbor <IP ADDRESS>  <INT ID>

This need to be done on both ends of the link, and will change the interface from sending out multicast hello messages to directed broadcasts, so you need to enter addition neighbour statements for each neighbour you want to connect to.

For some NBMA networks (such as frame relay) CISCO has added in a command to allow the router to forward the broadcasts over the link. It does this by sending a copy of the multicast/broadcast packet to each neighbouring router. This is needed for multipoint networks

#router(config-inf)#frame-relay  map IP <neighbour IP>  <Local DLCI>  broadcast

Now rather than using the neighbour command the router will forward any EIGRP hello’s across the to any routers configured with the broadcast command in there mapping.

Either of these two methods will allow the formation across the NBMA.

However there’s is now the issue of split horizon. Imagen you have a central router connected to two remote routers, each with there own routing tables. Split horizon says that a route update received on an interface will not be sent back out that same interface.  This means that if one of the remote routers sends an update to the central router, it will not then be relayed over to the second remote router.. To allow this to happen you must manually disable split horizon (it is disabled by default on a physical interface but enabled on sub interfaces). The command is as follows

router(config-inf)#no ip split-horizon eigrp <AS>

So recapping there is two parts to this, first allowing the hello messages across the NBMA, and then insuring the updates get copied to all routers.

These problems mainly occur when using the multipoint method, using point to point (although requiring more IP addresses and subnetting) avoids both the split horizon issue and the non broadcast issues, and is generally the recommended option.

DevilWAH

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