1. Install and configure FTP server in Red Hat/Centos 7.5 Linux

Step 1: Install vsftpd (very secure FTP daemon) package.

yum install -y vsftpd ftp


Step 2: Enable FTP on firewall

firewall-cmd –permanent –zone=public –add-service=ftp
firewall-cmd –reload


Step 3: to automatically start FTP Server when server powers on.

  1. enable vsftpd service.

systemctl enable vsftpd.service

2. Checking the status of ftp server

systemctl status vsftpd.service


Step 4: Configure vsftpd package. Edit /etc/vsftpd/vsftpd.conf

nano /etc/vsftpd/vsftpd.conf


  1. Change the line which contain anonymous_enable=NO to anonymous_enable=YES. This will give permit any one to access FTP server with authentication. If this setting is changed to ‘NO’, then users must use their login and password to access files from their home directory. [Note: For our use, I am keeping this setting as YES, so each user has to log in access their own files]
  2. local_enable=YES
    c. write_enable=YES
  3. Add the following to the end of the file.







Step 5: Start FTP Server
systemctl start vsftpd.service


Step 6: Verification. Create a file under ‘var/ftp/pub’. Use a web browser to access the file.

[root@localhost /]# find . -name “pub”

find: ‘./run/user/1000/gvfs’: Permission denied


[root@localhost /]# cd var/ftp/pub

[root@localhost pub]# nano ftppubfile1.txt


If anonymous_enable=YES, ./var/ftp/pub Directory will be used.


If anonymous_enable=NO, users have to login with their credentials to access files.



CCNP DC – 642-997 DCUFI Exam, DnD

Hope this will help you to prepare for 642-997 DCUFI exam.


Q1. DC Design Layer Characteristics



Q2. Cisco Nexus Design Layer and Features



Q3. Cisco Nexus Product Family Features



Q4. FCoE Protocol and Fibre Channel features



Q5. VSAN and SAN Zoning


Good luck to your study everyone! 🙂


GNS3 1.4.2 and IOU VM.ova Installation Tips

Assumption 1: You’ve already have a VMware Workstation or Virtual Box installed and running on your PC/Laptop
Assumption 2: You’ve already downloaded GNS3 1.4.2 and GNS3 VM.ova files from “https://github.com/GNS3/gns3-gui/releases”.
Now Let’s get started:

Step1: Import “GNS3 VM.ova” file on your VMWare Workstation or Virtual Box

Step 1a: Upload IOU L2 and L3 image files on “”, under IOU
Step 1b: Upload CiscoIOUKeygen.py file on “”, under IOU

Step2: Install GNS3 1.4.2
Step 2a: complete basic GNS3 setup following YouTube videos.
One of the videos is as below: https://www.youtube.com/watch?v=1j4VHW-vvR8

Step3: SSH into your IOU VM machine, and go to “/etc” folder and run the following commands under respective folder.
(Video Reference: https://www.youtube.com/watch?v=V0SdjK5tEcA)

Tip: Default IOU VM UID = gns3
Default IOU VM PWD = gns3

Required commands:
echo -ne \\x1\\x0\\x0\\x0 > /etc/hostid
echo -ne \\x1\\x0\\x0\\x0 > /etc/ioukey
echo hostid = 0000001 ; echo hostname = gns3-iouvm ; echo ioukey = 3d9

Step 4: Go to and upload CiscoIOUKeygen.py file

Step 5: Go to /opt/gns3/images/IOU directory and take ownership of the unloaded keygen file

Step 6: use python or python3 command to generate your 16 character long IOU key

root@gns3vm:/opt/gns3/images/IOU# python CiscoIOUKeygen.py
hostid=00000001, hostname=gns3vm, ioukey=25f

Add the following text to ~/.iourc:
gns3vm = acf51841caabfb0f;

You can disable the phone home feature with something like:
echo ‘ xml.cisco.com’ >> /etc/hosts

***Notice that my VM machine works with python command but not python3 command!!!

root@gns3vm:/opt/gns3/images/IOU# chmod +x CiscoIOUKeygen.py

## Notice that python3 command does not work here!!!!
root@gns3vm:/opt/gns3/images/IOU# python3 CiscoIOUKeygen.py
File “CiscoIOUKeygen.py”, line 11
print “hostid=” + hostid +”, hostname=”+ hostname + “, ioukey=” + hex(ioukey)[2:]
SyntaxError: invalid syntax

Step 7: Using the “gns3vm’ value, create a txt file containg the license information. Save the file as IOURC.txt and point your GNS3 remote server to this txt file.

gns3vm = acf51841caabfb0f;

CCNA Data Center 640-911 DCICN – Note 18, IPv6 Introduction

This is my first blog in 2016, I have been on holiday mode as I have been on one the longest annual leave in my life. Hope you understand the family commitment when you and your kids are on summer holiday (here in Sydney, Dec/Jan/Feb is blazing summer).


IPv6, the history and does it really matter to you or anyone?

The simple answer is YES, then why? The single biggest driver behind the development and introduction of IPv6 is  a long prediction of lack of usable IPv4 IP addresses since the explosion of World Wide Web (www) in 1995. The www development goes back to 1991 and then the introduction of grandfather web browser, Mosaic was first introduced in 1993. By year 1995, one third of IPv4 addresses were consumed, by year 2000, half of all IPv4 addresses were use.

As reviewed in previous notes, IPv4 consists of 32 bit address structure and theoretically that should give us 2 to the power of 32 IP addresses, that is 4294967296 IP addresses or roughly, 4.3 billion IP addresses . But not all IP addresses are usable such as the reserved IP addresses for private network use as well as the Class E addresses reserved for development and testing purposes. In other words, only around 2.5 billion IP addresses are true usable addresses. If you just check out our world’s population today ( http://www.worldometers.info/world-population/, China = 1.407 billion and India = 1.2912 billion people,), just looking at top two countries’ population figures, you can feel the IPv4 address shortage on your skin. The trend is that the world’s network has been doubling in size every year for the past 15 years. (https://en.wikipedia.org/wiki/IPv4_address_exhaustion)

With the advancement of new technologies comes the rapid deletion of available IPv4 IP addresses. Anything that’s related to mobile communications and entertainment as well as all other areas seems to be needing more and more IP addresses for everyday use. In the past, it was expected that all the IPv4 addresses would be depleted by 2011 but it is 2016 and we are still using IPv4 address without much thought, all thanks to the counter measures put into place to slow down the IPv4 IP address deletion. e.g.) The fine art of sub-netting, a practical use of DHCP and IP Natting.


 Quick note on history of IPv6:

1990 – IETF had predicted that all class B IPv4 IP addresses will be deleted by 1994
1991 Nov – IETF formed  ROAD (ROuting and ADress) Group in Santa Fe, US.
1995 – IPNG (IP Next Generation) Workgroup had written and submitted ‘RFC 1883’, this RFC has become the foundation of current IPv6.
1996 – 6Bone was introduced. 6Bone was a test-bed for IPv6 vulnerabilities connecting 57 countries across 1100 sites.
1999 – IPv6 Forum was launched to standardize the use of IPv6
2006 Jul 06 – 6Bone was decommissioned after 10 years of testing.
Current – Majority of IP products are manufactured with IPv6 capabilities and compatibility. IPv6 is slowly phasing out IPv4 around the world.

Source: https://en.wikipedia.org/wiki/IPv6


Quick note on 10 Advantages (Characteristics) of IPv6:
1. Larger IP address space than IPv4, 32 bits based IPv4 vs 128 bits based IPv6
2. Better end-to-end connectivity than IPv4
– peer-to-peer application connections such as games, video conferencing, file sharing and VoIP
– No need to use NAT as the shortage of addresses is thing of IPv4
3. Plug-n-Play feature of IPv6
– plug-and-play auto-configuration, e.g.) DHCPv6
4. Simplified Header structures leading to faster routing
5. Better security features
– use of IPSec (a built-in feature)
6. Improved QoS features
7. Improved Multicast and Anycast abilities
8. Better mobility features
9. Ease of administration over IPv4
10. IPv6 follows the key design principles of IPv4

Source: http://www.ipv6.com/articles/general/Top-10-Features-that-make-IPv6-greater-than-IPv4.htm

In the next section, we will look at some characteristics of IPv6 and then in the final section of IPv6, I will demonstrate IPv6 in a simple lab. Happy blogging, reading and all the best with your learning and career in 2016.

The planet of Network APEs : Part 2.2 Hybrid Router on a STICK Lab

OK, let’s have some fun with our lab set up! First, let’s configure a quick proof of concept lab, ‘A hybrid router on a stick’:

Router on a stick 1

Preparation for above lab:

1. Install and prepare two virtual machines, mine is called winxp2 and winxp3. I created one and cloned it to make them as two separate VM’s

2. On VM Workstation 11, add two more VM networks. I have added VMnet3 and subscribed winxp2 to it, and added VMnet4 and assigned winxp3 to it. Make sure you disable DHCP services as below screenshots:

Router on a stick 2Router on a stick 3

Router on a stick 4Router on a stick 5

3. Tweak your GNS3 – IOU configuration so, we can add virtual machines and connect them to the topology. This is a very important step, so make sure you get these steps 100%. Go to ‘Edit’ –> ‘Preferences’ and change your settings per screenshots below:

Note: My IOU VM IP is, your could be different, so please check.

Router on a stick 8

Router on a stick 6Router on a stick 7

Configure your Local and Remote servers as above.

4. Now Open GNS3 and add the following devices.

a. Add Cisco IOU router and rename to iR1

b. Add Cisco IOU switch and rename to iSW1, connect e0/0 to iR1’s e0/0

c. Drag and drop a cloud, change the name to wxp2, change icon to PC. Configure network interface by adding VMnet3. Now, since we cannot connect the cloud directly to the iSW1’s interface, we need to use a dummy switch to connect these two devices. This is a very important step, so just drop a GNS3 switch and connect wxp2’s interface to SW1’s port 2, then SW1’s port 1 to e0/3 of iSW1.

d. Similarly, for wxp3, repeat the process described as in c using their respective ports.

e. Drag and drop two VPCS (GNS3 built-in) and connect their e0’s to switchports on iSW1. This time, there is no need to use dummy switches.

So at the end of above exercise, you should have a connection similar to the following diagram:

Router on a stick 9

Now the configuration of iR1 and iSW1.

iR1 config:

e0/0 sub-interface configuration:

interface Ethernet0/0
no ip address

no shutdown
interface Ethernet0/0.1 <<<This is for VLAN 1 (wxp2 and PC1)
encapsulation dot1Q 1 native
ip address
interface Ethernet0/0.2 <<<This is for VLAN 2 (wxp3 and PC2)
encapsulation dot1Q 2
ip address

DHCP configuration for VLAN 1 and VLAN 2:

ip dhcp pool ONE
ip dhcp pool TWO

iSW1 config:

vlan 2
name CCNA
interface Ethernet0/0
switchport trunk encapsulation dot1q
switchport mode trunk
duplex auto
interface Ethernet0/1
duplex auto
interface Ethernet0/2
switchport access vlan 2
switchport mode access
duplex auto
interface Ethernet0/3
switchport mode access
duplex auto
interface Ethernet1/0
switchport access vlan 2
switchport mode access
duplex auto

interface Vlan1
ip address
ip default-gateway


Router on a stick 10

5. Now, on PC1 and PC2, run ‘ip dhcp’ command to obtain IP addresses from DHCP server on the router, iR1.

PC1> ip dhcp
PC2> ip dhcp

6. Next, check IP addresses of your Windows Virtual Machines, if everything have been correctly connected and configured, your windows machine also should get the IP addresses from the DHCP server, iR1.

wxp2 IP Address:

C:\Documents and Settings\john>ipconfig

Windows IP Configuration
Ethernet adapter Local Area Connection 2:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . :
Subnet Mask . . . . . . . . . . . :
Default Gateway . . . . . . . . . :

wxp3 IP Address:

C:\Documents and Settings\john>ipconfig

Windows IP Configuration
Ethernet adapter Local Area Connection 2:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . :
Subnet Mask . . . . . . . . . . . :
Default Gateway . . . . . . . . . :

7. Now ping IP addresses and verify your PoC lab. You should be able to ping at all IP addresses and also, RDP from one windows machine to another. Have a fun!

Router on a stick 11

Router on a stick 12

The planet of Network APEs : Part 2.1 Vmware workstation, IOU and GNS3 installation and configuration

Following Part 2.0, here is a simple steps to install and configure your Cisco IOU router and switch lab on GNS3.

1 – Install VMware Workstation 11

Download VMware Workstation 11 and install it on your Laptop.

2- Download GNS3 IOU VM.ova appliance

Download GNS3 IOU VM.ova from http://sourceforge.net/projects/gns-3/files/IOU%20VMs/GNS3%20IOU%20VM.ova/download

3 – Install the GNS3 IOU VM

First, import GNS3 IOU VM.

Second, optionally upgrade your GNS3 IOU VM from the OS CLI using ‘pip3 install gns3-server==1.0beta2’ command.

For upgrade to take place, your VM’s network interface must be bridged to your PC’s internet network interface. After the completion of the upgrade, restore VM’s network interface to host-only network.

4 – Configure the VM Network in VMware Workstation 11

Use the following screenshot as your reference point.

Tip: Make the starting IP of DHCP server as


5 – Start the GNS3 IOU VM

Log into IOU OS CLI. For OS CLI of GNS3 IOU VM User ID is ‘root’ and password is ‘cisco’

Check the IP address of your IOU server using ‘ifconfig eth0’

Check the server service is running by using ‘ps aux | grep gns3server’

6 – Upload L2 and L3 IOU images

Browse to

Remember your L2 image path for your switch use.


Remember your L3 image path for your router use.



If you don’t have L2 image, download one from the following Google search results:


If you don’t already have L3 image, download one form the following Google search results:


Or, from here:


7 – Create a file with an IOU license key Or download already made IOU license key

Option 1: If you already have a genuine licence key. Create a text file called ‘iourc.txt’ and cut and past the following contents, save.


gns3-iouvm = xxxxxxxxxxxxxxxx;

Option 2: If you don’t have a key, then your next option is to find a key on the net.

Download it from http://forum.gns3.net/topic9032.html

Now create a folder under C:\ called IOURC and save the file under the newly created folder.


8 – Putting it all together

Launch GNS3 and go to Preferences à Server à Remote Servers and add your VM IP address ( as a Remote Server. Then click ‘Apply’ and ‘Save’.


9 – Add the IOU license key file

On the same Preferences menu, go to ‘IOS on Unix’. Clicke to iourc.txt file path under ‘General Settings’


10 – Add L2 and L3 IOU devices

Add L2 and L3 IOU devices on GNS3. Each time you add a device, click ‘Apply’ and ‘OK’.



11 – Testing your IOU image

Configure a simple lab and run your testing. Now you are ready to go.


Note: If you are having issues opening up the upload web page for IOU images, please use WinSCP and drop both L2 and L3 images into “/home/gns3/GNS3/images”:

Protocol: SCP

Port: 22

UID: root

PWD: cisco


The planet of Network APEs : Part 2.0 Welcome back GNS3 and thank you Cisco for leaking out IOU!

Welcome back Network Apes! It has been extremely busy with work, study and family. I was having trouble finding time to write something useful for anyone who is interested in or studying Cisco Technologies. Even to get to the point of writing this post, I had to spend about 10 days familiarizing myself with the idea of using GNS3 GUI as an application, this was due to the painful memories of sitting in front of my PC, trying to fix some silly old GNS3 bugs and also my preference of Dynamips over old GNS3. At one stage, it did not make sense to me to use very very buggy old GNS3 over Dynamips, it was not worth my time and pain to work with old GNS3 and its million bugs.

As I have discussed in earlier posts, I have come across Cisco Web-IOU and its support for almost full set of Cisco IOS commands in a virtual environment, Wow… Cisco IOS on Linux virtual server running (exactly emulating) IOS 15.x and also, providing close to real L2/L3 switch experience (not the crappy NM-16ESW module as in Dynamips/old GNS3)!!! You can see that the new GNS3 and IOU have a serious potential to help networking students and Engineers to use their time and money for better things.

Initially, testing out the IOU, I used the Web-IOU and it is pretty impressive in its own ways but soon ran into limitations. How do I connect some virtual machines running on the same host machine to the virtualized IOU network? Thanks to many others who also labbed, documented and shared their guides on how to do things, there were lots and lots of documents, some very useful but most of them rubbish as I have been trying to do this on a Windows 64bit machine! Yeah, go ahead and laugh at me and the 95% of the PC users, I was trying to do this on a windows machine, specifically a laptop, you can find my PC specs and the items you will need to set you up for hundreds of free and very interesting Cisco/Microsoft/Linux labbing.

Guess what I have discovered after hours of Google search? “Your IOU will have to be integrated with the newer version of GNS3!” On initial discovery I thought “WTF, GNS3? Oh No, not again!!!”. I was totally disappointed with the truth and challenge I was facing. Yes it is still very useful and free of charge, but still extremely temperamental like a red-haired, nose pieced and rocking rolling gf on redbull on Vodka, it has totally eaten up my whole weekend with many hours of pain, I even took this problem to my sleep so I can solve the problem in my dreams. Only after 3 days of struggle I was able to set up something useful working with both IOU and new GNS3. Please see the picture below to understand what I have been trying to do in last 3 days. A very simple bus topology lab, which will serve any Networking student and Engineers the basic foundation you need to do many labs in a single PC or laptop. I will close this post with just an introduction to what was required to set this lab up and then share with everyone the step-by-step configurations in the trailing posts.

GNS3 IOU 002

The topology is simple and expandable, the connection is as below:


  • PC1 is a Windows 8 VMware workstation VM.
  • PC2 is a Windows 7 VMware Workstation VM.
  • SW1  and SW1 are IOU L2 switch.
  • R1 and R2 are IOU routers.

Lab hardware & software used:


  • ASUS K53SD with i7 2670QM CPU, 128GB SSD, 8GB DDR3 memory