Archive for October, 2007

No luck…

Tuesday, October 30th, 2007

… and a day which was wasted. I just spent like 6 hours getting VMWare, installing Fedora and setting up Dynamips on my Windows XP just to find out that performances are pretty much like running it on Windows. I might try this again when I find an Intel VT capable processor or get me an AMD (like that is going to happen :P ). One thing you should know is to set mmap = false since it uses it than to push much faster (although still not fast enough for me).

Anyways guess its back to the drawing board and dual-booting Fedora and XP. Until next time, truly yours :)

Squeezing flash…

Monday, October 29th, 2007

Today I ran into something I have not seen before. While doing rounds on my D/D simulations I tried

>vlan database
>vtp server

And I got an error that said something like “can’t change to server, can’t write squeeze log”, and I was like WHAT? After researching and finding out what is wrong I managed to correct everything by

>delete vlan.dat
>erase flash:

But had to recreate VLANs on the switch which was not all that hard.
Hope it helps someone.

P.S. When I tried to recreate the problem I just was not able to. Loading new labs and everything, there  is something freaky about this!!!

VMWare workstations does not work on Windows XP x64…

Sunday, October 28th, 2007

… at least not as it should be. Today I was hoping to get another instance of Fedora 7 x64 installed on my computer and this time within my XP x64 environment using VMWare. Alas VMWare 6.02 (the latest version to date) does not see my OS as a 64-bit system so than I can not install any x64 OSs on it.

Guess Vista is waiting for me. Luckily I was planning to install it anyway one day so I put aside a partition specially for that purpose. Now all I need is to get Vista :)   Bye Bye :)

Aliens are here, so give them … wireless!

Saturday, October 27th, 2007

This is a great game I use to have fun and learn about how some things in Cisco wireless world functions.

Take a look and have fun!

The game! 

Why should I go into networking?

Friday, October 26th, 2007

Personally when I decided to start my IT career it was not in networking but programming. Java was my poison and I felt really good. Programming is a nice gig if you love solving everyday puzzles and creating something. One problem with programming jobs is for me the lack of standards which I just mentioned in my last post.

Why are standards important you might ask? Well in case of Java and everything surrounding  it there were just too many application servers and frameworks. Which one was the right one? They were all the right one, every firm preferred another one which made your ability to switch firms very hard or at least a bit uncomfortable. Off course you could have been a freelancer and do what you like but thats another story.

My way into networking was accidental in a way. While serving my civil duty to the country I managed to snatch a course which helped me attain MCDST (Microsoft Certified Desktop Support Technician) and pass one of the two server exams  needed for MCSA (System administrator) on Windows Server 2003. I quickly took up books and some virtual machines and passed the complete MCSA track in march 2007 :) Not that far ago. From than on I have been slowly getting into the field and I wanted to get a better grip on network infrastructure and decided that CCNA is the best way to go. So with no experience with network equipment I started learning for the first of Cisco exams. Just fell in love with this, incredible how much more akin I felt to network administration than system administration. When its this good you just got to go on so I passed the BSCI and am now preparing for BCMSN (will hopefully take it in early november).

In the end perhaps the most important thing which draws me to Cisco is the exclusivity of the CCIE. Being an achiever and a  goal oriented person I just love a challenge and this just might be the ultimate one. I have already seen the CCIE blueprint and have made a great plan, pass CCNP and CCIP in 2008 (QOS, MPLS, BGP all needed in R&S CCIE) and the written in 2009 plus hopefully have a try at the lab by the end of 2009. Attainable? Probably! These are revised dates from what I was planning a couple of months ago and there will probably be more revisions as it is no easy task.

So if you are like me a challenge seeker please join me, would love to hear why you decided it would be great to be in networking. :)

Take care

A chump installing Fedora 7 x64 and Dynamips

Friday, October 26th, 2007

Well it was time! I have pushed Dynamips on Windows to its limits, the stack dumps are becoming too often. A couple of weeks ago I managed to pony up the cash for a new nice machine and decided the best thing would be to install Linux. Considering several distributions I opted for Fedora 7 x64 since it is one of the industry standards, and I really like those.

Installation is as smooth as it is with windows, no fuss you just click next next next and finish :) Watch out to format you hard disks nicely since formating and mounting for a newbie is a drag. So after that was finished it was Dynamips turn to be tackled. Blindhog has a great tutorial on how to install on linux and I used parts of his tutorial but downloaded and extracted everything from the GUI. My biggest problem was finding drivers for my NIC to be able to connect to the internet (luckily my old computer was still next to me connected). When you get everything installed and you start testing there is this great feeling that everything is smooth and you have 20% utilization of your processor when you start a full InternetworkExpert lab. Now the thing that took me some time to get was how to use Terminal server. If you are on only one NIC than you are in trouble as bridging will take away your internet, but lets get to the problem.

First thing you need to do is in your .net file specify a tap interface.

f0/0 = NIO_tap:tap0

than you need to bring it up as well as your eth0 if it is not up, keep both interfaces with no IP adresses

yum install bridge-utils #install bridge utilities so you can make a bridge interface
ifconfig -a #shows you all your interfaces
ifconfig tap0 up #brings tap0 interface up
brctl addbr br0 #creates bridge br0
ifconfig br0 netmask #adds this ip adress to your br0 interface
brctl addif eth0 #adds interface to bridge
brctl addif tap0 #adds interface to bridge
ifconfig -a #to check if everything is well setup

Now you should be able to start up TermServ from IE topology and connect from it to your other routers/switches with no problem. If you run into some kind of problem try first checking your connectivity between Fedora and TermServ by either pinging from host or from TermServ.

Take care and hope you have fun :)


Wednesday, October 24th, 2007

How many VLANs can you have?
There are several VLAN ranges that are in effect. First and foremost there are VLANs 0 and 4095 which are reserved for system use only. Than you have the default VLAN 1, can not be modified or deleted. Important thing to know is that you can change your default VLAN on a switch, so it is not always the case that 1 is default. VLANs 2-1001 are regular VLANs which can be used normaly, 1002-1005 are FDDI and token ring VLANs and cannot be deleted. In the end there are extended VLANs which range from 1006 to 4094 which are normally not available for use.

Whats a native VLAN?

A native VLAN is a the default VLAN for every port that is not assigned one and a must when configuring a 802.1Q trunk. When you have a trunk link and if you want it to communicate well it is imperative that you have the same native VLAN on both sides of your trunk. In dot1q trunking packets which travel the link untagged (since each packet is tagged with a VLAN number) are understood by switches as native VLAN packets, so you see if two switches understand differently which is native you can have a real mess on your hands with the link not forming.
Why are VLANs important, can they be good and bad?

VLANs help us separate parts of a network. Every VLAN is a new broadcast domain which helps prevent broadcast storms. Unkown MAC unicast traffic is a problem in large networks where switches who don’t know the receiver flood the packet to all ports. Finding and isolating problems is much easier in a nicely designed VLAN so why not have it :)

How should you divide your VLANs?

Depending on your needs you can separate it geographically or by business function, its all up to you and your needs.

What is an end-to-end VLAN?

This is a term usually associated with a geographically dispersed network where people which are far apart belong to the same VLAN. Another good thing that is characteristic of an end-to-end VLAN is that as a user moves it remains in the same VLAN no matter where he is.
What is a local VLAN?

A local VLAN is constricted to a single building usually and is always routed away to reach other networks. It does not extend beyond the Building distribution module.
Three layers of a hierarchical network?

Access - switches connected to users

Distribution - routers connecting parts of the network

Core - fast switching, no routing for best performance
VLAN config modes?

Logicaly global config mode. Another mode to configure is “vlan database” mode which is great for use with Dynamips/Dynagen simulator if you need switching modification. This mode is getting deprecated and will be kicked out soon from IOSs.

Types of ports on a switch?

Access port - connecting to a user

Trunk port - connecting two switches, switch and a router or switch and a trunk-capable network card

VLAN trunks?

A way to push more than one VLAN through a link. Every packet is tagged/encapsulated as it goes through the link.

ISL vs dot1q trunking?

ISL is Cisco proprietary and does not play with others. Dot1Q is cross-vendor. The first encapsulates frames and second tags them. Tagging a frame in dot1q can lead to “giants” a frame that exceeds the 1518 byte maximum size because it adds another 4 bytes with the tag.
VTP domains?

VTP management domains are a great way to more easily administer more switches at once. When several switches are in the same domain you can change configuration on the “server” switch and all other will follow through and change also.
VTP server/client/transparent status?

Three modes connected to management domains are:

server - commands client switches

client - listens to server

transparent - listens to no one but forwards orders from servers
VTP pruning?

A way to discover whether  switches are over using their links and leaking traffic where they should not. When pruning is done every time a flood is going to a particular VLAN, the switch will not flood it to subnets where there is no one using that VLAN.
Trunk link negotiation?

Several modes of trunk link negotiations exist:

auto - will accept someone trying to establish a trunk

desirable - will attempt to make a trunk

access - will never become a trunk

trunk nonegotiate - no DTP packets will be sent so you must setup  the other side as a trunk to get one

Well used a little help :)

Hope it helps.

BCMSN top down view!

Wednesday, October 24th, 2007

BCMSN as one of the requisites for CCNP is all about switching. There is a lot of new stuff for me as I have not yet gotten into switching that much. Wireless and network security is also included and from what I have seen makes up around 30-40% of the material on the exam. Lets dissect the topics.

Implement VLANs. We have already seen VLANs in CCNA preparations and if you passed the BSCI there was some talk there also. This time VLANs come back with a vengeance, but they are not all that hard. Lets pump up some questions about VLANs.

  1. How many VLANs can you have?
  2. Whats a native VLAN?
  3. Why are VLANs important, can they be good and bad?
  4. How should you divide your VLANs?
  5. What is an end-to-end VLAN?
  6. What is a local VLAN?
  7. Three layers of a hierarchical network?
  8. VLAN config modes?
  9. Types of ports on a switch?
  10. VLAN trunks?
  11. ISL vs dot1q trunking?
  12. Native VLANs?
  13. VLAN ranges?
  14. VTP domains?
  15. VTP server/client/transparent status?
  16. VTP pruning?
  17. Trunk link negotiation?

Niiiice! That should be enough for VLANs, I will consider myself sufficiently versed in VLANs if I can answer all this from my head.Look at the answers here!

My first serious rack rental

Monday, October 1st, 2007

I have previously tried out Mindtech communications rack rental for the CCNP just because I was too lazy to find an IOS that had IS-IS capabilities. It worked nicely and for $14 you get 20 x 1 hour sessions. The schedule is mostly empty so you can fit in usually the same day.

Now for the serious part of this article. Yesterday I had my first meeting with and it was a good one. I always wonder what the time is and some of these rack rental vendors don’t even give you “at this moment its blah blah blah hours and minutes here”, sure they tell you what time zone it is. A programmer will take 2 minutes to build in that into a site and really that is a must. So Tony Schaffran has a +1 in my book for that. Next comes the directions and logging in experience which was as smooth as it could be no problems there. I had a small mishap with getting confused with all the connections so lost some time there but everything was where it was supposed to be. Got my Putty die on me a couple of times but may be to my hectic keyboard typing :)

A 5.5 hours session is $15 if you take 10 and is closer to the cheap part of the rack rental spectrum with under $3 per hour. Why did I start with this provider? Smaller sessions and VISA card payments. I just can’t believe that it is so impossible to implement something other than PayPal (which I can’t use since my third world country still does not support) so kudos for that too. And 11.5 hours is just too long for me, I get brain malfunctions with these 5 hours anyway. Guess practice makes perfect, so will have to practice more.

All in all a very nice experience and surely a service worth returning to.

Take care :)