Enterprise Network on GNS3 – Part 5 – Data Center

The article is the fifth of the series of the articles discussing the enterprise network configuration. The article focus on the Data Center (DC) configuration. DC consists of the two devices - Server1 and the switch vIOS-Ser-I. Of course, the DC network with a single switch and the server is far away from any known DC network design. Typically, modern horizontally scaled large-size Layer 3 DCs consist of thousands of servers connected to the Top of Rack (ToR) l3 switches and they follow leaf and spine design. The DC of this size can be hardly emulated on a single PC. For this reason I only share the configuration of the Cisco L3 switch that is located in our DC. The switch is running Cisco vIOS-L2, version 15.2 and it has assigned 768MB RAM by GNS3.

The switch vIOS-Ser-I connects Ubuntu Linux Server to DC network. The configuration of the services such as bonding, NTP, DHCP, Syslog-ng, DNS and RADIUS running on the server is explained in more details later.

Picture 1 - Data Center

Note: The configuration file of the device vIOS-Serv-I is attached here.

1. Switch vIOS-Ser-I Configuration

Rather than explaining every line of the configuration, we Continue reading

Digital DVB-T on Raspbian

Recently, I have been asked to get working Digital Video Broadcasting - Terrestria (DVB-T) tunner on Raspberry PI 3. The tunner is Cinergy DVB-T stick from Terratec. Below are my notes describing installation of the stick on Raspbian Linux 9.1 Stretch. I hope someone find them useful.

1. Copy Raspbian to SD CARD (on Ubuntu)

First, we need to copy Raspbian installation image to SD card. Below is the example using dd command on Linux.

$ sudo dd bs=4M if=2017-09-07-raspbian-stretch.img of=/dev/mmcblk0 status=progress conv=fsync

Insert SD card to Raspberry and power on the box. The default user is pi with the password raspberry. Enable SSH and VNC server for remote box administration. Navigate to Menu-> Preferences-> Raspberry PI Configuration.

2. Install Firmware

Inspect kernel for any error message connected with DVB-T tunner.

$ dmesg

Picture 1 - Missing firmware isdbt_rio.imp

Download firmware file isdbt_rio.imp (md5 - 9b762c1808fd8da81bbec3e24ddb04a3) from here. I have also uploaded it to Google disk. You can download and copy the file to the directory /lib/firmware with the command below.

$ sudo wget https://drive.google.com/uc?id=1MwDGSG4ZEm3eeJuf0gS686Be-ngx4rKR -O /lib/firmware/isdbt_rio.inp

Reboot PI and check kernel for any other kernel error messages.

Picture 2 - Continue reading

Raspberry Pi3 WIFI Router Based on Linux piCore

Recently I have bought a Christmas present for myself from GearBest, costing only $49,21 USD. It includes Raspberry Pi 3 single board computer along with 2.5A power supply, case and several heat sinks. Pi3 is the latest and the most powerful Raspberry model, equipped with 1.2GZ 64-bit ARM processor, 1GB RAM and integrated 10/100 Ethernet port and Wifi 802.11n. Although I can simply use it as a cheap desktop computer, I have different goal in my mind.

Six years ago, I built my own SOHO router/switch base on Intel Pentium III - 733Mhz. It was working great but to save electricity consumption I have never used it in production. However, I have never completely given up idea to build and use my own  router. It comes true thanks to Raspberry Pi3 computer as it consumes maximum 1.34 A or 6.7 W under stress when peripherals and WiFi are connected.

Picture1 - Raspberry Pi 3 Model B
Source: http://fosssig.com/tinkerers/1-raspberry-pi-and-kodi/

To shorten the story, I have built a wifi router that runs piCore 9.0.3 on Raspberry PI3. The clients are connected via wireless network to the router that runs hostapd. The hostapd is configured Continue reading

Linux PiCore on Raspberry Pi – First Steps

The blog post contains notes about the installation of piCore Linux on Raspberry Pi 3 computer. The related topic is well known, discussed by many similar posts however the article represents my own copy & paste reference for later usage.

The first generation of Raspberry Pi 1 has been with us since February 2012. Recently in version 3B, the Pi3 is equipped with 1.2 GHz 64-bit quad-core ARM Cortex-A53 processor, 1 GB of RAM and it has integrated 2.4 GHz WiFi 802.11n (150 Mbit/s), Bluetooth 4.1 (24 Mbit/s) on Broadcom BCM43438 chip. It also provides the integrated 10/100 Ethernet port. These factors along with the cheap price (~ 35 US), small size (~ 85.60mm x 56mm x 21mm), low weight (~ 45g) and low power consumption (maximum 1.34 A or 6.7 W under stress when peripherals and WiFi are connected) makes this single-board computer ideal candidate for use in the recent Internet of Things (IoT) world.

Raspberry Pi can run several OSs built for ARM architecture such as Windows 10 IoT Core, Raspbian (based on Debian), Ubuntu Mate and many others. The Linux distributions offer either full desktop environment or they are released Continue reading

Enterprise Network on GNS3 – Part 4 – Cisco ASAv-I

This is the fourth from the series of the articles that discuss configuration of the enterprise network. The article explains configuration of the device ASAv-I. The device is a Cisco Adaptive Security Virtual Appliance (ASAv) version 9.6(1) installed on qcow2 Qemu disk. The ASAv-I provides traffic filtering and inspection services for the campus network and Data Center (DC). It also connects the campus network and DC to the vIOS-EDGE-I edge router.

Picture 1 -  ASAv-I,  Campus, DC and  Edge Connection

Note: The recommended RAM size for ASAv instance is 2048 MB. In order to lower memory consumption,  GNS3 is configured to assign 1536 MB to the ASAv.

Note: The interface eth0 on the ASAv-I is referred as the interface Management0/0 in ASAv configuration. The interface eth0  is not connected as we use the inside interfaces for management instead. The first connected interface is then the interface eth1 that is referred as the interface GigabitEthernet0/0 in ASAv CLI. Similarly, the second connected interface eth2 is referred as the GigabitEthernet0/1 and so on.

Note: Here is the configuration file of vASA-I.

ASAv-I Configuration

Once we start ASAv, the Qemu window is launched. However we want to use GNS3 Continue reading

VyOS 1.1.8 Released

More than one year after publishing a previous VyOS version, the new VyOS 1.1.8 is finally released. VyOS is an open source network operating system that can be installed on physical hardware or as a virtual machine. It is based on GNU/Linux and joins multiple applications such as Quagga, ISC DHCPD, OpenVPN, StrongS/WAN and others under a single management interface. VyOS is a cheap and effective solution for those who want to learn Junos like CLI.

Linux user can use my installation scripts for zero-touch VyOS deployment. Scripts download the newest stable VyOS x86-64 Live ISO image from web, create VMware VMDK disk and install VyOS from ISO on the disk. The scripts are available here (part 1.1).

Picture 1 - VyOS Version 1.1.8

Note: The scripts are tested on Linux with installed Qemu, KVM and Expect. First,  run the Bash script deploy vyos.sh. The script downloads the latest VyOS ISO image. Then run the Expect script install vyos.exp  that  install on VyOS Live CD.

FRRouting Software with EIGRP Support

In September 2016 I wrote the article about EIGRP support in Quagga network routing suite. More than one year later, I am going to check the progress of development EIGRP in Linux again. To do so, I have installed a fork of Quagga -  FRRouting (FRR) with EIGRP support on Linux Core. EIGRP routing daemon included inside FRR benefits from active development brought by Cumulus employees. For the purpose of FRR testing, I have created a minimalistic Linux Core Pure64 virtual machine  with FRR suite compiled as frr extension. Meanwhile, I have submitted FRR extension so it will be available in the next few days in Tinycore repository.

Content of Disk - CorePure64-frr_3-1.vmdk:

• Linux Core Pure 64 version 8.2,kernel 4.8.17
• FRRouting 3.1dev
• OpenSSL 1.0.2l 25 May 2017
• OpenSSH_7.2p2
• GNU bash, 4.4.0(1)
• iproute2-ss140411
• iptables v1.4.21
• tcpdump 4.7.4
• Nmap 7.12
• mtr 0.86
• hping 3.0.0-alpha-1
• iperf 3.1b3
• D-ITG 2.8.1 (r1023)

Software:

• Host OS - Ubuntu 16.04.3 LTS x64
• GNS3 2.0.3
• QEMU x64 emulator version 2.8.0

Picture 1 - Network Topology

The FRR EIGRP instance with attached CorePure64-frr_3-1.vmdk Continue reading

Enterprise Network on GNS3 – Part 3 – Distribution and Core Layers

This is the third from the series of the articles that discuss configuration of the entire enterprise network. The article focuses on the configuration of the distribution and core switches. The distribution layer consists of two multilayer switches vEOS-DIS-I and vEOS-DIS-II. The switches are Arista vEOS version 4.17.2F Qemu appliances installed on VMware disks. Each appliance has assigned 1536 MB RAM.

The distribution switches route traffic between end user VLANs and they connect the lower layer network to a Core layer. The layer 3 (routed) interfaces connect both distribution switches to each other and to the Core switches.  The interfaces toward the Access layer are layer 2 (switchports). The OSPF routing protocol is running on the distribution switches so there is only l3 connectivity between distribution and core layer.

Picture 1 - Distribution and Core Layers of Enterprise Campus Network

Note: The configuration files of the distribution switches are: vEOS-DIS-I and  vEOS-DIS-II.

The core layer consists of the switches vIOS-Core-I and vIOS-Core-II. These are the Cisco vIOS-l2 Qemu appliances on qcow2 disks, version 15.2. Each switch has assigned 768 MB RAM by GNS3. The core layer is completely layer3. It si connected to the lower Continue reading

Enterprise Network on GNS3 – Part 2 – Access Layer

This is the second from the series of the articles that discuss a complete configuration of the enterprise network. Our enterprise campus network consists of the core, distribution and access layer. This network infrastructure design is called a three-tier network model. Each layer has specific function. The access layer provides access for end users to the network . They are two access switches located inside the access layer. The access switches OpenSwitch-Acc-I and OpenSwitch-Acc-II are OpenSwitch Qemu appliances installed on VMware VMDK disks. The switches run OpenSwitch network OS version 0.4.0 and they have assigned 1024 MB memory by GNS3. More details about building OpenSwitch appliance prior to version 2.0 can be found here.

The ports Ethernet 3 a and 4 on both switches are configured as access ports and they connect PC1 and PC4 to the campus network. The ports Ethernet 1 and Ethernet 2 are uplinks that connect access switches to the distribution switches. They are configured as trunk ports, carrying traffic from multiple VLANs. Thanks to redundant uplink connection, the access switches remain connected to the upper layer, even in case of the failure one of the distribution switches.

Picture 1 - Access Switches Connected Continue reading

Enterprise Network on GNS3 – Part 1 – Introduction

Several months ago I had created a simple GNS3 network topology for practicing my networking skills. What had firstly begun as a simple lab, later grew in to a real world enterprise network consisting of a campus, data center, DMZ network blocks and ISPs. During the next several weeks I added new devices into the topology, struggling with no time due to complicated family circumstances. In March 2017 I completely stopped working on this project. Luckily, I was done with the configuration of all devices and I wrote several articles describing my progress. Now, almost a half of the year later, I am ready to share my experience with the blog readers and publish the articles. Below is the list of the articles. I hope you find them useful.

Enterprise Network on GNS3 - Part 1 - Introduction
Enterprise Network on GNS3 - Part 2 - Access Layer
Enterprise Network on GNS3 - Part 3 - Distribution and Core Layers
Enterprise Network on GNS3 - Part 4 - Cisco ASAv-I
Enterprise Network on GNS3 - Part 5 - Data Center
Enterprise Network on GNS3 - Part 6 - Edge Router and ISPs
Enterprise Network on GNS3 - Part 7 - Continue reading

Downloading YouTube Videos From Links Saved In Google Chrome Bookmarks

The Bash script youtube-bookmarks-mp3.sh is using Python youtube-dl script along with ffmpeg in order to download videos from YouTube service. It also enables youtube-dl to convert videos to mp3 audio format. The script exports YouTube links from Bookmarks and copy them into the file bookmarks.txt. Multiple videos are downloaded and converted simultaneously in the background by the script.

Note: According to YouTube Terms of Service, you shall not copy, reproduce, distribute, transmit, broadcast, display, sell, license, or otherwise exploit any Content for any other purposes without the prior written consent of YouTube or the respective licensors of the Content.

OpenSwitch Network Operating System

The Open Network Install Environment (ONIE) is an open source install environment that gives a switch user a choice to download ONIE compliant Network Operation System (NOS) to bare metal network switches. The OpenSwitch is community based, open source NOS that runs on hardware based on ONIE.

The goal of this article is to show how to build OpenSwitch Virtual Machine appliance, describe its capabilities and to introduce three methods for managing OpenSwitch. The OpenSwitch VM appliance was created by OpenSwitch project for training and testing purpose. It uses software data plane to forward the packets but it is not intended to be used as a virtual switch for connecting virtual machines. OpenSwitch supports many L2, L3 protocols such as STP, LACP, LLDP, OSPF, BGP, DHCP, TFTP, NTP, SSH, SNMP and others. These protocols run as separate daemons and they were integrated from another open-source projects.

For instance Quagga project provides L3 functionality to Openswitch. Quagga modules ops-ospf and ops-bgp update active routes in OpenvSwitch database (OVSDB). The module ops-zebra reads routes from OVSDB and install them to the kernel. Static routes are also stored in OVSDB, read by ops-zebra module and installed to the kernel. In order to use Continue reading

Syslog-ng Configuration For Newbies

Some time ago I was asked by my friend to recommend a cost-free solution that he could use for storing logs of his security device over network. The Linux OS with installed syslog-ng is perfectly suitable for this job because it can collect logs from any source, process them in near real-time and deliver them to a wide variety of destinations. However it was challenge to explain all the steps in an easy manner as he was a total newbie in a Linux world. For this reason I wrote a basic installation and configuration manual for him which I share with you. The manual helps you to setup syslog-ng on Ubuntu server and troubleshoot the possible issues.

1. Install Ubuntu 16.04 Server Edition

During Ubuntu installation you are asked to provide the username/password and IP settings. Once an installation process finishes, the system is rebooted. when you get your console again, login and install updates with the command:

$ sudo su
# apt-get update
# apt-get upgrade

2. Install and Configure Syslog-ng

# apt-get install syslog-ng

First, you need to download a simple configuration file that I created for you.

# cd /etc/syslog-ng/conf.d
# wget http://brezular.com/wp-content/uploads/2016/12/firewals.conf_.txt -O firewals.conf
# Continue reading

Reverese Shell on Linux

Reverse shell is technique when a client connects to a server and the client provides its shell to the server. Clients is typically a host hidden behind the NAT or a firewall having an access to the server but not vice versa. Thanks to a reverse shell the server controls a client's shell having an access to the client's network even the client is hidden behind the NAT. They are several methods how to create a reverse shell used depending on software available on the client. I will show how to create a reverse shell using SSH, Ncat and Bash.

Picture 1 - Network Topology

Picture 1 shows our testing topology. The client (Ubuntu Server 16.04) is located behind the NAT with the IP address 192.168.1.4/24. The server (Kubuntu 16.04) has assigned the IP address 172.17.100.7/16.

1. Reverse Shell Using SSH Reverse Tunnel

This method is based on the fact that the client has knowledge of the server SSH login credentials and vice versa. SSH server must be running on both the server and client. Client must be allowed to access server through firewall.

Client:
$ ssh -R 10000:127.0.0.1:22 [email protected]. Continue reading

Bash Script for Converting Video To MP3 Audio

I like listening to video training on my smartphone while walking to work. To save the space on the memory card I convert videos to MP3 audio in advance. For this purpose I wrote a Bash script video_to_mp3.sh which helps me to manage a conversion job. The script uses ffmpeg for conversion and it creates parallel conversion tasks to speed up the conversion process. The script checks the CPU load and it creates a new background process only if the CPU load is under a particular limit entered by a user.

Picture 1 - Script Usage

Below is the output from the conversion process.

Picture 2 - Output From Conversion Process

The script creates a log file displaying info about the result of all conversion tasks. If the conversion fails for a particular video file, the script displays a return value of ffmpeg utility and the name of the file which is not successfully converted.

Picture 2 - Output from Log File

End.

GRE over IPSec Tunnel and NAT Between Cisco and VyOS

The goal of this tutorial is to provide a configuration for Cisco and VyOS network devices with configured PAT (Port Address Translation) that connect two remote sides A and B through point-to-point GRE tunnel encapsulated into a IPsec tunnel. In a previous tutorial we proved that GRE tunnels in conjunction with IPsec tunnels transmit multicast traffic while data integrity, authentication and confidentiality was in place. I also provided a simple configuration of GRE, IPsec tunnel and OSPF routing protocol on the Cisco and VyOS routers. In this tutorial I will go further and provide full configuration of  the all network devices including PAT and access-lists.  

Picture 1 - Network Topology

Topology Description - Side A

Each side has a Layer 2 Cisco switch located in a LAN network. A switch connects hosts to its switchports. Each switchport is assigned to a particular VLAN. For instance, a host PC1 is connected to the switch SW1 and the switchport is assigned to a VLAN 100. Hosts in VLAN 100 (subnet 192.168.1.0/24) have guaranteed access to a remote subnet 192.168.2.0/24 via GRE/IPsec tunnel. A NAT access-list configured on a router R1 ensures that IP address of the host in VLAN 100 is not translated by PAT when a destination address is Continue reading

Scripts

This article contains a list of scripts that I created and that are somehow useful for me. You are free to download and modify them according to your needs. I do not take any responsibility for improper use or any damage caused by using them.

1. Networking & Servers

1.1 Automatic Deployment VyOS ISO on VMware VM
A Bash script deploy vyos.sh downloads the latest VyOS ISO image and an Expect script install vyos.exp installs VyOS ISO on VMware vmdk disk.

1.2 Automatic Deployment of DRBL (Clonezilla) Server
The script deploy drbl.sh  installs and configure DRBL server on Ubuntu with a single Ethernet card. You have to provide the name of Ethernet interface as an argument. The script creates a virtual interface for you based on a physical interface. It also downloads a DRBL project public key, download and install drbl package from repository.

1.3 Secure Copy with Rsync from SSH server
The script copy.sh keeps copying files with rsync command while a return value of the rsync command is not zero. Just edit script and set server IP address and bothe remote and local directory.

1.4 Collecting MAC and IP addresses Continue reading

Hacking DRBL Client PXE Boot Password

In a previous tutorial I showed installation of Clonezilla Server Edition on Ubuntu using my own Bash script. We configured PXE (Pre eXecution Environment)) password for clients so when the clients booted a password had to be entered to startup. This tutorial explains two different ways how to get and crack the PXE boot password.



Picture 1 - Client Requires to Enter PXE Password During Startup

First, we should mention some facts. The PXE client password is stored in plain text in a configuration file /etc/drbl/drblpush.conf. The password is secretpassword and it can be found in a dictionary rockyout.txt.

Picture 2 - Plain Text PXE Client Boot Password

The same PXE client password is stored as a hash in a file /tftpboot/nbi_img/prelinux.cfg/default.

Picture 3 - PXE Client Boot SHA-1 Base64 Encoded Salted Hash

The hash is created by utility /usr/sbin/sha1pass on DRBL server. It is a Perl script which takes two arguments from STDIN - a password and salt and it creates SHA-1 base64 salted hash.

Picture 4 - Perl Script fo Generating Hash from Password and Salt

Explanation:

• $4$ - SHA-1 base64 encoded salted hash
• 2mNryVVj - salt
• WIWlkNc6cA9+eQqcf9xU0d5IvVQ - hash

They are several methods how to obtain PXE boot Continue reading

Clonezilla Server Edition Installation on Ubuntu

The tutorial describes installation steps for Clonezilla Server Edition (SE) on Ubuntu 16.04.1 LTS using a Bash script. Clonezilla is OpenSource Cloning System (OCS) and it is a partition and disk imaging/cloning program . It helps you to do system deployment, bare metal backup and recovery. Two types of Clonezilla are available, Clonezilla live and Clonezilla SE (server edition).

Clonezilla live is suitable for single machine backup and restore. Clonezilla SE is for massive deployment because it can clone many computers simultaneously. Clonezilla saves and restores only used blocks in the hard disk. It decreases time and saves the hard disk space and increases the clone efficiency.

Clonezilla is a part of DRBL (Diskless Remote Boot in Linux) which provides a diskless environment for client machines. Therefore we need to install and configure DRBL server first. I created DRBL deployment script deploy_drbl.sh that helps you to install DRBL and configure server on Ubuntu with a single Ethernet card. You have to provide only the name of Ethernet interface and the script creates virtual interface for you based on your physical interface. It also downloads a DRBL project public key, download and install drbl package from repository. The script starts interactive Bash and Perl scripts that come with Continue reading

Using Rsync to Copy Files From SSH Server

Recently I have come through an interesting problem. I needed to download a raw copy of the HDD image located on a remote server (about 180GB) connected via  1 Mbps link. Network connection dropped frequently so the requirement was to reestablish connection automatically, without my intervention.

Definition of Terms
Server - a remote computer with an IP address 172.17.100.5/16 which contains a raw copy of the HDD image - a file /root/ubuntu.iso.
Client - a local computer that copies a raw copy of the HDD image from the server.

Below is my how-to which helped me to fulfill a task. I hope it might be useful to you.

1. Create Multiple Archive Files
The idea is to create a compressed archive file and to split it to multiple sequential chunks in order to make transfer of files less depended on network outages due to an unreliable link.

$ tar cvf - ubuntu.iso | gzip -9 - | split -b 10M -d - ./disk/ubuntu.tar.gz.

The command tar creates a tar archive from a file ubuntu.iso and send it to a standard output instead to the file. The command gzip compress everything from a standard input using the best compression ratio (parameter -9) and send Continue reading