OSPF in my own words

OSPF is a link state protocol, it does not exchange routes and metrics. The only thing that OSPF exchanges is the state of it's link and the cost associated with the link. As link state advertisement arrives from OSPF neighbors, the OSPF routers perform a series of computation on the LSA's and this gives the OSPF router a complete picture of the Network.

Shortest path first Algorithm(SPF). This is the series of computation performed by OSPF routers on received link state advertisement. Once the computation is complete, the result is what you see when you execute the command:
#Show ip ospf database

Before any LSA's adjencency is formed a neighbour relationship must be formed or must be discovered, LSA's are only sent if there is a change in the link status.

Running GNS3 0.6.1 on Mac OS X

GNS3 0.6.1 on Mac OS X

Below is the Steps required to install and run GNS 0.6.1.

Here is the Step by step guide.

Method 1.

1. Install the Apple Devs Tools (on your Mac OS X DvD or download it on ADC account).
2. Download python 2.5.1 (or higher) for MacOS X on http://www.python.org/download/ and install it.
3. Download qt-mac-opensource-4.3.4.dmg on http://trolltech.com/developer/downloads/qt/mac and install it.
4. Download SIP http://www.riverbankcomputing.com/Downloads/sip4/sip-4.7.tar.gz, compile and install it.
5. Download PyQt hhttp://www.riverbankcomputing.com/Downloads/PyQt4/GPL/PyQt-mac-gpl-4.3.tar.gz, compile and install it.
6. Start GNS3.


Method 2.

Download the DMG package, it includes two binary versions of Dynamips: one for OSX Tiger and the other for OSX Leopard.
Obviously Method 2 is out of the question. Method 1 is also a bit unclear for people with no compiling experience.

Let’s start from the top.

1. Install the Apple Devs Tools (on your Mac OS X DvD or download it on ADC account).

If you don’t have an ADC account, Use your Leopard DVD if you have any. Open the Optional Installs folder and you will see the Xcode Tools folder. In that folder, run and install XcodeTools.mpkg.

2. Download python 2.5.1 (or higher) for MacOS X on http://www.python.org/download/ and install it.

This step is pretty straightforward. Download, mount, and install from the .dmg file. For reference, I grabbed the 2.6.2 disc image.

3. Download qt-mac-opensource-4.3.4.dmg on http://trolltech.com/developer/downloads/qt/mac and install it.

The link is no longer active, but a quick google search yielded a few download sources. I grabbed qt-mac-opensource-4.3.4 from here. http://www.python.org/ftp/python/2.6.2/python-2.6.2-macosx2009-04-16.dmg"

Again, mount and install from the .dmg disk image.

4. Download SIP http://www.riverbankcomputing.com/Downloads/sip4/sip-4.7.tar.gz, compile and install it.

Unfortunately, all the riverbankcomputing.com links in the README are invalid. This is where I grabbed sip 4.7. http://service-spi.web.cern.ch/service-spi/external/tarFiles/sip-4.7.tar.gz

After downloading the file, we come to the fun part.

Open terminal and cd into the folder you downloaded the tar file and compile via the following commands:


Macintosh:$ tar xvzf sip-4.7.tar.gz
Macintosh:$ cd sip-4.7
Macintosh:sip-4.7$ python configure.py
Macintosh:sip-4.7$ make
Macintosh:sip-4.7$ make installHopefully everything ran smoothly and installed without a hitch.

5. Download PyQt hhttp://www.riverbankcomputing.com/Downloads/PyQt4/GPL/PyQt-mac-gpl-4.3.tar.gz, compile and install it.

I couldn’t find 4.3, so I downloaded 4.3.1 from here.

Again, run the following commands to decompress and compile PyQt.

Macintosh:$ tar xvzf PyQt-mac-gpl-4.3.1.tar.gz
Macintosh:$ cd PyQt-mac-gpl-4.3.1
Macintosh:PyQt-mac-gpl-4.3.1$ python configure.py
Macintosh:PyQt-mac-gpl-4.3.1$ make
Macintosh:PyQt-mac-gpl-4.3.1$ make installPretty simple and it should look a lot like step 4.

We’re now in the home stretch.

6. Start GNS3.

Grab the tar from the GNS3 homepage. We have one last step here, which is basically just decompressing the tar file.

Macintosh:$ tar xvzf GNS3-0.6.1-src.tar.gzThat’s it. We’re done! If you look in the folder you just created, you will see a GNS3 executable. Run it and GNS3 will launch.

What’s great is it pulled all my settings from GNS3-0.5 so I did not have to mess with configuring and setting up directories, idle values, etc.

I hope this has been useful and let me know if anything is unclear.

VLAN

Learn How to configure Cisco Routers

How to configure Router on a Stick aka 802.1q This is a Cisco Web Blog that will help you learn how to Design, Configure and Manage a Cisco router.

The first technology that we are going to try and master will be VLAN.

I guess the best way to start learning about VLAN is from configuring Router on a Stick.

Before you can configure Router on a Stick you need to know what a VLAN is

What is VLAN ?

What is Vlan and what does it mean to a non technical person ?. VLAN stands for Virtual Local Area Network. It's a way of virtually separating a switch physical ports into different Logical Networks an each Nework behaving as if they were configured on a different Logical Switch.

The diagram above shows 2 VLANS configured on a switch connected to a router. This is known as Router on a Stick. This Layer 2 Cisco switch carries two VLANs (VLAN 10 – RED and VLAN 20 – GREEN) with two hosts connected on them as shown on the diagram above. The first host belongs to Network 10.10.10.0/24 (VLAN10) and the second one to 20.20.20.0/24 (VLAN20). By default, if the switch is just a normal Layer 2 switch the two hosts can not communicate between them because they belong to different VLANs and there is no routing between the 2 VLANS.Howevere, if we want to provide network connectivity between the two VLANs we need to have a Layer 3 device somewhere in the network. We can either do this with a layer 3 switch or a router. In this example I will use a router to provide Layer 3 connectivity as shown in our diagram.

The router uses just a single interface connected to a trunk port on the switch. The Router interface can be divided into two subinterfaces, with each subinterface belonging to the appropriate VLAN. The switch port connected to the router must be a trunk in order to be able to carry both VLANs towards the router port. Lets see the configuration below:

SWITCH CONFIGURATION

(config)# vlan database
(config-vlan)# vlan 10 name RED
(config-vlan)# vlan 20 name GREEN
(config-vlan)# exit
(config)# interface FastEthernet1/0/1
(config-if)# description trunk-to-router-on-a-stick
(config-if)# switchport trunk encapsulation dot1q
(config-if)# switchport mode trunk
(config-if)# exit
(config)# interface FastEthernet1/0/2
(config-if)# description connection-to-RED-VLAN
(config-if)# switchport mode access
(config-if)# switchport access vlan 10
(config-if)# exit
(config)# interface FastEthernet1/0/3
(config-if)# description connection-to-GREEN-VLAN
(config-if)# switchport mode access
(config-if)# switchport access vlan 20
(config-if)# exit
(config)# exit
# copy run start

ROUTER CONFIGURATION
# conf t
(config)# interface fastethernet 0/0.10
(config-if)# encapsulation dot1q 10
(config-if)# ip address 10.10.10.2 255.255.255.0
(config-if)# exit
(config)# interface fastethernet 0/0.20
(config-if)# encapsulation dot1q 20
(config-if)# ip address 20.20.20.2 255.255.255.0(
config-if)# exit

Now, in order for the two hosts to communicate between them, they must set as default gateway the IP address of the corresponding router subinterface address (e.g for host in VLAN 10 the gateway must be 10.10.10.2 and for host in VLAN 20 the gateway must be 20.20.20.2).

What is a Trunk ?

A trunk according to Cisco is a link that can carry frames for more than one VLAN
at once. A trunk can also be used to connect two switches so that devices in either VLAN can talk to device in the second switch in the same VLAN. When we talk about VLAN in most intances we are talking about Switches, However, Routers's can also connect to VLAN'S as Mentioned above (Router on a Stick).