SerureCRT 8.3 installation on Ubuntu 16.04LTS Linux

This tutorial uses SerureCRT 8.3 - Nov 9, 2017 release running on Ubuntu 16.04LTS machine, follow the steps below and enjoy fully featured rock-solid terminal emulation:

• Download the latest SecureCRT for Linux Ubuntu 16.x 64-bit (scrt-8.3.0-1514.ubuntu16-64.x86_64.deb) from official Website 
• Double click the downloaded .deb file, and install it through Ubuntu Software Center for ease.
• Open a terminal (Ctrl+Alt+t) and download the perl script:
  rana@Ubuntu16:~$ wget http://download.boll.me/securecrt_linux_crack.pl
• Check out the SecureCRT installation path:
  rana@Ubuntu16:~$ whereis SecureCRT
  SecureCRT: /usr/bin/SecureCRT 
• Run the perl script on SecureCRT's installation path '/usr/bin/SecureCRT':
  rana@Ubuntu16:~$ sudo perl securecrt_linux_crack.pl /usr/bin/SecureCRT
  If the script is successful, the registration information output will be generated in terminal.
• Now, run 'SecureCRT' command in terminal and follow the prompts to fill out the registration information output in 'Enter License Manually' Tab.
• All Done!

(Script share is just for the sake of testing/educational purposes and do not endorse cracking, use in production or intend to violate any copyrights. Please, properly give credits to the developers; download trial and buy the most awesome SecureCRT - Peace!)

HTH,
Rana Tauqeer.

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GNS3 2.0.3 Error on Ubuntu 16.04LTS: IOS/IOU_name.bin%20is%20not%20executable

GNS3 2.0.3 Error Message on Ubuntu 16.04LTS:

home/rana/GNS3/images/IOU/i86bi-linux-l2-adventerprisek9-15.6.0.9S.bin%20is%20not%20executable

Some fellows came across the above error, while adding/configuring IOS/IOU on GNS3 2.0.3 and the development version GNS3 2.1.0 running on Ubuntu 16.04LTS machines. The error message is self explanatory, and just needs you to add execution rights to the IOS/IOU files in GNS3's images directory, like below and can be repeated for all IOS/IOU giving the same error:

(The below example assumes GNS3's default directories, and shows rights inclusion to L2 IOU, L3 IOU and a c7200 router IOS, just open a terminal with Ctrl+Alt+t, and do the following from '/home/user' directory)

rana@Ubuntu16:~cd GNS3/images/IOU
rana@Ubuntu16:~/GNS3/images/IOU$ sudo chmod +x i86bi-linux-l2-adventerprisek9-15.6.0.9S.bin
[sudo] password for rana: 

rana@Ubuntu16:~/GNS3/images/IOU$ sudo chmod +x i86bi-linux-l3-adventerprisek9-15.4.1T.bin

rana@Ubuntu16:~/GNS3/images/IOU$ cd ..
rana@Ubuntu16:~cd GNS3/images$ cd IOS
rana@Ubuntu16:~/GNS3/images/IOS$ sudo chmod +x c7200-adventerprisek9-mz.153-3.XB12.bin
rana@Ubuntu16:~/GNS3/images/IOS$ 

Now, open GNS3 again and add the IOS/IOU again in Preferences Tab, everything should work as intended.


HTH,
Rana Tauqeer.

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GNS3 2.0.3 & GNS3 2.1.0 Error on Ubuntu 16.04LTS: uBridge is not available, path doesn't exist.

GNS3 2.0.3 ERROR:
"uBridge is not available, path doesn't exist, or you just installed GNS3 and need to restart your user session to refresh user permissions"

Solution:

I came across the above uBridge error, while running GNS3 2.0.3 stable version (also tried the development version of GNS3 2.1.0, but stuck at the same error), on my Ubuntu 16.04LTS Machine. Applied almost all available solutions on GNS3 forums and other blogs but nothing worked. Finally, I was able to figure out the following solution, which did the charm! 

Step-1: Open a terminal (Ctrl+Alt+t), and login as root/Superuser 
rana@Ubuntu16:~$ su - 
Password: 
root@Ubuntu16:~$

Step-2: Update repository 
root@Ubuntu16:~$apt-get update 

Step-3: Install 'sudo' 
While trying and working around other available solutions, I suspect that something went wrong with 'sudo' too, this step can be exempted/skipped if 'sudo' is working correctly for you - (which can be checked with 'sudo ls' command) 
root@Ubuntu16:~$apt install sudo 

Step-4: Add the user ('rana' in my case) to group sudo 
root@Ubuntu16:~$usermod -aG sudo rana 

Step-5: Reboot the machine
root@Ubuntu16:~$reboot

Step6: After reboot, reconfigure ubridge 
rana@Ubuntu16:~$sudo dpkg-reconfigure ubridge 

Step-7: Run GNS3, test it and enjoy learning!!! 

[The same answer and other suggested workarounds related to this particular error can also be found at GNS3 Community Forums]

HTH, 
Rana Tauqeer.

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Cisco Packet Tracer 7.1 Installation on Ubuntu 16.04 LTS Linux

Cisco Packet Tracer (CPT) is a free Network and IoT Simulation & Visualization tool for starters in Cisco Networking Technologies. Packet Tracer's 32bit & 64bit versions are available for Microsoft Windows 7, 8.1 and 10, and a 64-bit version is available for Linux (Not available for macOS at this time). This tutorial will focus on installing Cisco Packet Tracer 7.1 on Ubuntu 16.04.3 LTS (Same process is valid for all Debian Linux based Distros):

• Download Packet Tracer 7.1 from Cisco Networking Academy (NetAcad)
  (you must be a member of NetAcad to download CPT)
• Open a terminal (by pressing Ctrl + Alt + t), and change directory to the downloaded file location (/home/User/Downloads' in this case) and extract the downloaded .tar file :
  $ cd ~/Downloads
  $ tar -xzvf Cisco_PacketTracer71_64bit_linux.tar.gz

• Start the installation by typing '/.install' in extracted files directory:
  $ cd Cisco_PacketTracer71_64bit_linux
  $ sudo ./install
• You will be asked to read the terms (EULA):
  (Keep pressing 'Enter' key until EULA is read 100%)
• Now you'll be asked to accept EULA:
  Do you accept the terms of the EULA? (Y)es/(N)o(Press 'Y' to accept EULA)
• Enter location to install Cisco Packet Tracer or press enter for installation in default directory [/opt/pt]:
  (Press ‘Enter’ key to select the default location /opt/pt )
• Now, you'll be asked, Should we create a symbolic link "packettracer" in /usr/local/bin for easy Cisco Packet Tracer startup? [Yn] (Press 'Y' to create a symbolic link)
• After completion of installation, launch Packet Tracer 7.1 by typing ‘packettracer’ in terminal.
  $packettracer
  Starting Packet Tracer 7.1
• Enter your Cisco NetAcad Credentials to login or login as guest.
  
  
  

PS:

Some folks have reported that their Packet Tracer installation completed successfully, but 'packettracer' command didn't open CPT, and no error message was shown, like below: 
rana@Ubuntu16:~$ packettracer
Starting Packet Tracer 7.1
rana@Ubuntu16:~$ 
In this case, follow the below solution:

• Open a terminal, and download Debian package containing the older version of 'libicui18n' (CPT requires libicui18n with an older version '52' instead of '55', which is not available in Ubuntu16.04 LTS.)
• $wget http://security.ubuntu.com/ubuntu/pool/main/i/icu/libicu52_52.1-3ubuntu0.7_amd64.deb
• Install the .deb package
  $sudo dpkg -i libicu52_52.1-3ubuntu0.7_amd64.deb
• Now CPT should start correctly via 'packettracer' in a terminal.
  [Credits: Steve]

HTH,
Rana Tauqeer.

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Fascinating Box Up Time!

A fellow sent me a picture showing UP TIME of a Production Switch, the longest I have ever seen!!!!

 Box UpTime of 19years; just inplace upgrades, never reloaded or lost power, isn't it fascinating? How much more have you seen?

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Clock Rate or Clocking

Clock rate/Clocking is actual line speed and is configured on serial links in DCE side of network. When you set the clock rate for a serial interface, you are setting the speed of the interface, in other words, actual rate of data transfer. It has to do with the physical speed of the circuit (typically based on TDM architectures) where your clock cycle is 'x' times per second (deriving bandwidth of 'x' bits per second).  You can't send at speeds greater than your clock rate as this is a physical limiting!

The clock rate is used to match the clocks on the receiver and transmitter on remote and local router. The two routers need to sync up their clock perimeters in order to decode the packets coming on their interfaces.

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Ethernet Frame - Explained!

Ethernet Frame

The Ethernet frame structure is defined in the IEEE 802.3 standard. Following explains a typical Ethernet Frame and description of each field in the frame:

• Preamble – informs the receiving system that a frame is starting and enables synchronization. The Preamble consists of seven bytes all of the form 10101010, and is used by the receiver to allow it to establish bit synchronization (there is no clocking information on the Ether when nothing is being sent). This is a stream of bits used to allow the transmitter and receiver to synchronize their communication. The preamble is an alternating pattern of binary 56 ones and zeroes. The preamble is immediately followed by the Start Frame Delimiter. An alternating 1,0 pattern provides a 5 MHz clock at the start of each packet, which allows the receiving devices to lock the incoming bit stream.

• SFD (Start Frame Delimiter) – signifies that the Destination MAC Address field begins with the next byte. The Start frame delimiter is a single byte, 10101011, which is a frame flag, indicating the start of a frame. This is always 10101011 and is used to indicate the beginning of the frame information. The preamble is seven octets and the SFD is one octet (synch). The SFD is 10101011, where the last pair of 1s allows the receiver to come into the alternating 1,0 pattern somewhere in the middle and still sync up to detect the beginning of the data.

• Destination MAC – identifies the receiving system. This is the MAC address of the machine receiving data. This transmits a 48-bit value using the least significant bit (LSB) first. The DA is used by receiving stations to determine whether an incoming packet is addressed to a particular node. The destination address can be an individual address or a broadcast or multicast MAC address. Remember that a broadcast is all 1s—all Fs in hex—and is sent to all devices. A multicast is sent only to a similar subset of nodes on a network.

• Source MAC – identifies the sending system. This is the MAC address of the machine transmitting data. The SA (Source Address) is a 48-bit MAC address used to identify the transmitting device, and it uses the least significant bit first. Broadcast and multicast address formats are illegal within the SA field.

• Type – defines the type of routed protocol inside the frame, for example IPv4 or IPv6. 802.3 uses a Length field, but the Ethernet_II frame uses a Type field to identify the Network layer protocol. The old, original 802.3 cannot identify the upper-layer protocol and must be used with a proprietary LAN—IPX, for example. The Type field for IPv4 is 08-00, mostly just referred to as 0x800 in hexadecimal, and 0x86dd for IPv6.

• Data and Pad – (aka Payload) contains the payload data. Padding data is added to meet the minimum length requirement for this field (46 bytes). This is the length of the entire Ethernet frame in bytes. It is rarely larger than 1500bytes as that is usually the maximum transmission frame size (MTU) for most serial connections. Ethernet networks tend to use serial devices to access the Internet. The data is inserted here. This is a packet sent down to the Data Link layer from the Network layer. The size can vary from 46 to 1,500 bytes.

• FCS (Frame Check Sequence) – contains a 32-bit Cyclic Redundancy Check (CRC) which allows detection of corrupted data. This field contains the Frame Check Sequence (FCS) which is calculated using a Cyclic Redundancy Check(CRC). The FCS allows Ethernet to detect errors in the Ethernet frame and reject the frame if it appears damaged.FCS is a field at the end of the frame that’s used to store the cyclic redundancy check (CRC) answer. The CRC is a mathematical algorithm that’s run when each frame is built based on the data in the frame. When a receiving host receives the frame and runs the CRC, the answer should be the same. If not, the frame is discarded, assuming errors have occurred.

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