Copper Loop Qualifications and Troubleshooting Line Impairments

The following factors are affecting the performance of a copper pair and problems are increasing with the higher frequencies involved in ADSL/VDSL. The below conditions, should be tested when delivering  a new service or during fault diagnosis.

• Return Loss
• Insertion Loss
• Longitudinal Balance
• Crosstalk
• Noise
• Interruptions
• Split Pairs
• Gauge Changes
• Bridge Taps
• Bad Cable Twisting

Installing TFTP server atftpd in Linux

I need a TFTP server to keep configurations files. I need the server to be simple to setup and be able to send or receive any file without any restrictions. It would be for a lab environment so a strict security is not necessary. I'm using Linux Mint.
In Linux I could find three different TFTP servers: 

• tftpd
• atftpd
• tftpd-hpa

Already tried tftpd see my other post Installing TFTP server in Linux. A minor problem is that you cannot transfer a file to the TFTP server.

Installing atftpd

sudo apt-get install atftpd

Remote console with a Mikrotik

I was testing the remote console feature on my Mikrotik (RB951G-2HnD). Detailed information posted on Mikrotik wiki on Manual:Port.

If you want to access serial device that can only talk to COM ports and is located somewhere else behind router, then you can use remote-access.

As defined in RFC 2217 RouterOS can transfer data from/to a serial device over TCP connection.

Enabling remote access on Mikrotik is  easy , see the steps below.

PLUG IN THE USB-TO-SERIAL ADAPTER

As soon as you plug in the USB-to-Serial Adapter you will see all available port and how they are used.  

3G Backup on Mikrotik

I was playing with my Mikrotik at home (RB951G-2HnD) trying to learn more stuff and though I should put of some use to my 3G USB dongle (HUAWEI E220). This came in handy as next day my main connection had problems and needed a backup connection to the Internet.

PLUG IN THE MODEM

Plug the 3G USB dongle and check on Mikrotik using the CLI commands "system resource usb print". If it can recognize the 3G modem then you are ok .See the command output below :

QinQ with Cisco Catalyst switches

Below a simple topology using QinQ tagging (officially known as IEEE 802.1ad or unofficially IEEE 802.1 QinQ ) on Cisco Catalyst C3550 switches.

C-VLANS 10 and 20 come from customer side and are encapsulated in the S-VLAN 1800.

This feature is also called VLAN double tagging or Vlan stacking, or Nested VLANs (Allied Telesis) or vMAN technology ( Extreme Networks).

VirtualBox in GNS3 under Linux part2

Continuing the previous post  VirtualBox in GNS3 under Linux part1, I will show below the steps on how to make GNS3 work with Virtualbox using emulated VirtualBox host-only adapters. 

STEP 1 : Install VirtualBox and VMs
Install VirtualBox (current version is 4.3.6) and your favorite Virtual Machines.

VirtualBox in GNS3 under Linux part1

Following my previous post on Installing GNS3 v0.8.6 on Linux , now will make GNS3 work together with VirtualBox.

By the time GNS3 started supporting VirtualBox virtualization ( v0.8.1 ), things were made easier in using VMs in GNS3. You just tell to GNS3 which VMs to load. see below the steps in detail. For more info see GNS3 website.

Later ( easy installation ) it became even simpler and no need any more to start GNS3/VirtualBox in root access mode.

STEP 1 : Install VirtualBox and VMs
Install VirtualBox (current version is 4.3.6) and your favorite Virtual Machines.

802.1Q VLAN trunk in Linux

I need to configure an Ethernet interface as an IEEE 802.1q VLAN trunk on Linux Mint for Lab purposes so I can connect GNS3 with a physical Cisco Switch. So I will create 6 vlan interface using VLAN ID 101-106 on eth0 interface.

Install VLAN package

 sudo apt-get install vlan