Category: networking

Monitoring your Network

so i guess „monitoring“ is about two things: availability and performance: detect performance bottlenecks get informed if parts (harddisks) / servers have failed / are about to fail security: detect, report and (if possible) automatically fence off „unusual“ network activity […]

NMAP basic network scanning – overview over LAN

What computers are online? What services/ports in what versions are online/open? over poorly or not so poorly documented LANs you can get an overview by using nmap. yum install nmap; # centos/redhat apt-get install nmap; # debian/ubuntu # get a […]


tested on: hostnamectl Static hostname: DebianLaptop Icon name: computer-laptop Chassis: laptop Operating System: Debian GNU/Linux 8 (jessie) Kernel: Linux 3.16.0-4-686-pae Architecture: x86 i assume you have your laptop/pc LAN connected to a switch/router and your default network card is eth0. […]


per default debian is not configured to forward traffic. on server/router/gateway: ping; # make sure internet connection works ifconfig eth0:0 netmask up; # add additional ip vim /etc/sysctl.conf # Uncomment the next line to enable packet forwarding […]


with tcpdump you can monitor IP packages, UDP packages, ICMP (ping). zypper install tcpdump; # comes preinstalled in suse12 apt-get install tcpdump; # debian8 yum install tcpdump; # centos7 redhat tcpdump -i eth0 tcpdump -vnni eth0; # very verbose root@Debian8:~# […]


show the ARP cache every network interface card (NIC)/LAN network card has a unique-as-possible vendor-asigned MAC address in the format 00:15:5d:00:07:08 this address is changeable like this: ip link set dev eth0 down; ip link set dev eth0 address 00:15:5d:00:07:09; […]


simple but usefull – you have the ip address of an computer in your local LAN – but you don’t know it’s computername. for internet-usage the host command is usefull because it shows – if a website is reachable by […]

IPv4 CIDR Subnet Mask Notation

IPv4 CIDR Subnet Mask Notation The CIDR number comes from the number of 1’s in the subnet mask when converted to binary. The common subnet mask is 11111111.11111111.11111111.00000000 in binary. This adds up to 24 1’s, or /24 (pronounced […]


Private IPv6 address range If you have multiple locations/sites/networks, you should assign each one a different „Subnet ID“, but use the same „Global“ ID for all of them. The IPv6 address space is so huge (2128) that everyone should be […]


IPv6: Goodbye to broadcast, say hello to Multicast » IPv6 while broadcast sends the traffic to all computers in the network – multicast follows a „subscribe to service“ model. broadcast -> a computer using ARP sends a packet to FF:FF:FF:FF:FF:FF […]


tested and works accross the following systems: uname -a Linux debian 3.16.0-4-686-pae #1 SMP Debian 3.16.39-1+deb8u2 (2017-03-07) i686 GNU/Linux uname -a Linux centos 3.10.0-514.el7.x86_64 #1 SMP Tue Nov 22 16:42:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux uname -a Linux suse […]


you can check your machine’s current ip with: ip addr show to modify your network interface address setting simply use the nmtui tool: this failed me once with „no Update2“ method… so let’s move on to the… manual way: terminal […]


Hardware Assembly: (i think 512MByte should be enough, 1GByte probably pretty good) Software Installation: including squid-proxy and web advertisement-filtering in the next part: OpenVPN 🙂 Thanks man! Amazing tutorials! by Related Links:


ip address add dev eth0 will add ip to your eth0 / LAN, in case you need to access more subnets than the default DHCP-subnet. please also checkout this amazingly cool youtube video tutorial on how to build […]

To Freifunk Firmware and Back on TP-Link TL-WR841N v11

Freifunk Erklärt / Flyer / Werbung / Aufkleber:  Freifunk_Erklärt_Aufkleber.pdf PLEASE SUPPORT THIS PROJECT! !UPDATE! WARNING! TP-Link TL-WR841N VERSION v13 DOES NOT WORK WITH OpenWRT or FREIFUNK FIRMWARE reasons below: problems with v13 and earlier are discussed here and not […]

16.11.2016 -> fire this up in a VirtualBox machine… using „Generic Linux“ settings. explanation later. as seen on: Firewall Router Zeroshell is a Linux distribution for servers and embedded devices aimed at providing the main network services a LAN […]


theoretically it should be possible to set a default gateway with ifconfig ifconfig [-a] [-s] [–help] [–version] {interface} [address] [netmask{address}] [gateway{address}] [tftpserver{address} ] [[up] | [down]] Set a fixed ip, activate network card and add default gateway this will: 1. […]


tested on: Linux Debian 3.16.0-4-686-pae #1 SMP Debian 3.16.7-ckt25-2+deb8u3 (2016-07-02) i686 GNU/Linux #install software #centos7 yum update && yum install samba-client samba-common cifs-utils #debian apt-get update && apt-get install cifs-utils mkdir /mnt/cifs; # create mountpoint mount -t cifs //FILE-SERVER-IP-ADDRESS/NAME_OF_SHARE /mnt/cifs […]


nmap returns a nice overview… but be aware! nmap localhost will return different results than nmap (actual ip of your host) – because not all services are allowed to be accessed from outside. in the following example smtp and […]


unfortunately things got changed in debian – but should also be valid throughout Debian 8.X. udev rules, persistent… whatever. why do people have to change stuff that actually works? it seems i am not the only one having this problem: […]