Archives for February 2014

I first want to thank the Cisco learning network. I noticed when I was building a home lab that my OSPF routes had been removed completely when I entered a static route on the router.

Originally I was thinking that doing an “ip route” command that I would see both the static route AND the OSPF route. Granted I knew that the OSPF route would take “back seat” to the static route but I thought I’d see both.

Before static route was entered:

After the static route was entered:

Question #1 – What would happen if we delete the static route?

Answer – After deleting the static route the router would INSTANTLY switch over to the OSPF learned route. The router doesn’t need to go out and get the info again since that route is already in the local OSPF database!

The command to see the OSPF info is:

show ip ospf database

What’s neat is if we turn on “debug ip OSPF rib” we can see the router instantly flicking that switch when the static route is removed.

I believe if you click on the last image it will show you the full resolution version.

Thank you Navneet! This post was made from the info he detailed on the Cisco Learning network and I took it from here: https://learningnetwork.cisco.com/docs/DOC-22414.

1. This document describes in detail, stable configuration details for GNS3 emulator. This is the configuration that works for me.

2. I faced several problems with GNS3 initially.

3. It turns out, once GNS3 is configured to work in a stable state, it is exceptionally wonderful and requires reasonably low system resources.

4. This documentation applies to GNS3 version 0.8.5 as on October 2013

Modifications:

Date – 07 Nov 2013

1. Added a section that describes a workaround to get the NW16ESW switch module to work with relevant routers

First:

The conclusion

1. Use the correct IOS images – It is a known fact that 2600 series images are not stable with GNS3

2. I can not provide the IOS images

3. Delay between routers boot – around 20 to 40 seconds

4. Malfunctioning module, as explained in point numbered 7: “slot 0: GT96100-FE”

Second:

Detailed configuration steps

• Table of contents:
• 1. Very important – IOS images
• 2. GNS3 Installation
• 3. Custom Directories – This stage can be skipped
• 4. Configuration of GNS3 – Preferences
• 5. Configure default IOS images and hypervisors
• 6. Configure “idle PC” value for router on first boot
• 7. Malfunctioning module
• 8. My computers configuration
• 9. baseconfig.txt
• 10. NM16ESW Workaround

 1. Very important – IOS images

These are the stable working IOS images for GNS 3. I have some of them as I own the routers.

i. Cisco 2691 Router | 2600 Series – Extremely stable

• c2691-adventerprisek9_ivs-mz.124-9.T7.bin

ii. Cisco 3640 Router | 3600 Series

• c3640-ik9o3s-mz.124-25.bin

iii. Cisco 3725 Router | 3700 Series – For MPLS

• c3725-adventerprisek9-mz.124-15.T5.bin

iv. Cisco 7200 Router – Extremely stable

• c7200-advipservicesk9-mz.124-2.T.bin
• c7200-advipservicesk9-mz.150-1.M.bin – For SLA

Note 1:

GNS3 crashes if the IOS image used is not compatible. One of the most incompatible and crash prone IOS image is of 2611XM series router. It is a known fact that 2600 series images are not stable with GNS3.

Note 2:

Once the IOS files have been procured, open them in WinRAR and extract the file. Use this expanded file with GNS3.

2. GNS3 Installation

Download the complete installer from the web site.  http://www.gns3.net/

Very useful: – After installation, locate the file named “baseconfig.txt”

• a. Normally it is located in the parent GNS3 installation folder.
• b. This is the default configuration that is applied to each router as it boots initially.
• c. This file path and name will be specified in “GNS3 – Edit – IOS images and hypervisors – base config: ………….” in step 5.
• d. Copy this file to the directory “C:\GNS3-Folders\IOS\” that is created in the next step.

I have also pasted the default baseconfig.txt that I use, at the end of this document. It can be used as is or with modifications.

3. Custom Directories – This stage can be skipped

The following steps describe how to create a custom directory, with minimized security settings, for storing GNS3 files.

• a. Create a “directory | folder” and name it “GNS3-Folders”.
•  b. Right click on this folder and select “Properties”. On the window that opens, point and click on “Security” tab
•  c. On this page, at the lower right, click on: – “Advanced” (For special permissions or advanced settings, click Advanced)
• d. Now “Permissions” tab must be open by default.  On this window, point and click on “Change Permissions…”  Uncheck – “Include inheritable permissions from this object’s parent”. On the warning that appears, select “Remove”.  Check – “Replace all child object permissions with inheritable permissions from this object”
• e. Click on “Add” – “Advanced” – “Find Now”. Click and select “Everyone”. Click “Ok” – “Ok”
• f. On the window that appears, confirm that:
  • i. Apply to:  “This folder, subfolders and files”, is selected from drop down list.
  • ii. Now, in the lower window, in front of “Full control”, check – “Allow” Click “Ok” – “Ok” – “Yes” – “Ok” – “Ok”
• g. Within this “GNS3-Folders” folder create the following four directories:
  • Capture
  • IOS
  • Projects
  • Temp
• h. Place the IOS files within the “GNS3-Folders\IOS” directory.
• i. Place the ‘baseconfig.txt’ file within the “GNS3-Folders\IOS” directory too.

4. Configuration of GNS3 – Preferences

From the menu bar, go to:

i. Edit – Preferences – General – (General settings)

Delay between each device start when starting all devices – 30 seconds

Autosave – 0 seconds

Paths:

• Projects directory: – “C:\GNS3-Folders\Projects – specify the path where you want the projects to be saved. I have configured the path to my thumb drive”
• OS Images (IOS, Qemu, PIX etc.) directory: – “C:\GNS3-Folders\IOS – specify the path where you have placed IOS images.”
• Configuration file: – Important.
• The path cannot be configured. However, note down the specified directory and after you have completely configured and checked GNS3, including ‘idle PC’ values, copy the gns3.ini to a different location.
• The complete configuration as well as specific idle PC values are retained in the gns3.ini file. Each time GNS3 is installed, only this file needs to be ‘imported’ and all the configuration is reinstated.

Caution – Paths are also reinstated along with rest of the configuration.

ii. Edit – Preferences – General – (Terminal settings)

Preconfigurated terminal commands:

• Select “Telnet (Windows)” from drop down list and then click on “Use” button
• Checked – “Close associated terminal programs when deleting a node”
• Unchecked – All the rest
• Delay between each consol when consoling to all devices: – 4 seconds

iii. Edit – Preferences – Dynamips – (Dynamips)

Executable path to Dynamips: – “Browse and specify the directory where dynamips.exe is located. By default it is within the GNS3 installation folder”

Working directory for Dynamips: – “Modify the path to point to the temp directory that was created within the GNS3-Folders folder”

Checked – “Automatically clean the working directory”

Unchecked – All the rest

Click on “Test settings” button and “Dynamips 0.2.xx-xxxx/Windows stable) successfully started” will be displayed in green.

iv. Edit – Preferences – Dynamips – (Hypervisor Manager)

Memory usage limit per hypervisor: – 512 MB

Checked – Allocate a new hypervisor per IOS image

Checked – Use Hypervisor Manager when importing

v. Edit – Preferences – Capture

Default Presets: – “Wireshark Live Pipe Traffic Capture (experimental) (Windows)”

Working directory for capture files: – “C:\GNS3-Folders\Capture”

Unchecked – Automatically start the command when capturing

5. Configure default IOS images and hypervisors:

From the menu bar, go to – “Edit – IOS images and hypervisors – (IOS Images)“

Common configuration for each IOS Image:

Image File: – “Browse and specify the path to IOS file”

i.

Base config:- “C:\GNS3-Folders\IOS\baseconfig.txt” – as explained in point 2.

Platform: c2691

Model: 2691

Default Ram: 256 MB

ii.

Base config:- “C:\GNS3-Folders\IOS\baseconfig.txt” – as explained in point 2.

Platform: c3600

Model: 3640

Default Ram: 256 MB

iii.

Base config:- “C:\GNS3-Folders\IOS\baseconfig.txt” – as explained in point 2.

Platform: c3700

Model: 3725

Default Ram: 256 MB

iv.

Base config:- “C:\GNS3-Folders\IOS\baseconfig.txt” – as explained in point 2.

Platform: c7200

Model: 7200

Default Ram: 256 MB

6. Configure “idle PC” value for router on first boot – this needs to be done only once for each router model

I have attached a video to this effect along with this document

• Drag and drop the router model into the workspace.

Right click – click “Start”

Right click – click “Console”

• Select the consol window that opens.

Press enter twice.

Wait till all on screen activity is over.

Close the console window.

• Right click on empty space on the windows taskbar at the bottom of the screen.

Select and click on “Start Task Manager”.

Point and click on the “Performance” tab.

Take a note of the CPU Usage – percent.

• Now in GNS3 workspace, where router is open, right click on the router.

Select and click on “Idle PC”

From the drop down list that will appear, select the value that has a  *  next to it.

If none of the values have a star, then select an average value.

Click – “Apply”

• Take a note of CPU Usage. If it has dropped down significantly, click on “Ok”.

Otherwise repeat with other values till an acceptable CPU Usage is attained.

Shut down the router and repeat for rest of the models.

7. Malfunctioning module

I have found that the following default FastEthernet module, which is pre-configured on slot 0: on some routers, is dis-functional.

I add another FastEthernet module for connectivity and do not use the default module at all.

This module does not work properly

slot 0: GT96100-FE

8. My computers configuration:

Processor: AMD Athlone X3

Motherboard: Asus

Ram: G-Skill 12 GB

9. baseconfig.txt

!

hostname %h

!

no ip domain lookup

ip domain-name lab.local

!

parser config cache interface

!

line con 0

exec-timeout 0 0

logging synchronous

privilege level 15

length 0

no login

line aux 0

exec-timeout 0 0

logging synchronous

privilege level 15

no login

!

!

10. NM16ESW Workaround

• I have not been able to use the NM16ESW switch module with its default settings to work as a switch
• However, I have discovered that if the port settings at both the ends – the module and the connected device – are modified to work at half duplex and speed of 10 Mbps, the module is functional.
• I have modified both the speed and duplex settings at the same time. However, it is very much possible that the module will work with just the modification of either one of them.

You may also simply add another router (preferably c1700) to your topology and configure it to act like a PC.

Just add a router and enter the following commands:

no ip routing !Turns off IP routing function
interface fa0/0 !Switches to FastEthernet interface
ip address address subnet_mask !Assigns IP address to Interface
no shutdown !Turns interface on
exit !Returns to global configuration mode
ip default-gateway gateway_address   !Config default gateway
ip http server !Optional – starts http server process

I like to change the ICON to look like a PC as well. You can right click the router and select: Change Symbol.

You might also want to check this out: http://www.gns3.net/documentation/gns3/adding-hosts-to-your-topologies/

This post will go over the answer I asked on my previous post. You can find the question here: http://jaredheinrichs.com/ccna-subnetting-static-routes-and-dhcp-relay-lab.html

The first thing you will need to do is to subnet the network. To do this we know we need at least 3 network that are as close to 50 as possible and two networks of 2 hosts.

Let’s write out the possible network groupings:

128    64     32   16    8   4    2    1

Because of this we know that we need 3 networks of “64” and two networks of “4”. (3x/26 and 2x/30)

64 gives us 62 potential hosts and 4 gives us 2 potential hosts.

Let’s do some sub-netting:

We know the first 4 “64” networks will start at these addresses:

• 0, 64, 128, 192

We know that the 4th network which is /30 will start at: 192. The next 3 /30 networks will look like:

• 192, 196, 200

Because we’ve done this simple things we can now subnet our network very easily!

Network #1

• Network – 192.168.1.0 /26
• Broadcast – 192.168.1.63
• Range – 192.168.1.1-62

Network #2

• Network – 192.168.1.64 /26
• Broadcast – 192.168.1.127
• Range – 192.168.1.65-126

Network #3

• Network – 192.168.1.128 /26
• Broadcast – 192.168.1.191
• Range – 192.168.1.129-190

Network #4

• Network – 192.168.1.192 /30
• Broadcast – 192.168.1.195
• Range – 192.168.1.93-94

Network #5

• Network – 192.168.1.196 /30
• Broadcast – 192.168.1.199
• Range – 192.168.1.197-198

Let’s look at the network map again:

Let’s open notepad ++ and write out the different configs on different tabs. Here’s my answer configs:

• r2-config
• r1-config
• r0-config

Keep in mind that you need to add Helper-addresses on r1 and r2