Category: networking

every once and a while… laptops and notebooks run out of battery… and when one manages to plug them in just 1% before stalling… the wifi on Debian might already be in hibernation and hardware on off does not help […]

about MAC address(es) not every switch has an IP assigned (if it has no web management interface, it does not need to) but it will have a MAC address. MAC address are per vendor and per device unique identifiers that […]

ONLY BUY FROM HARDWARE VENDORS THAT SUPPORT FREE & OPEN SOURCE SOFTWARE! (release the sources for their drivers and documentation for their hardware) “Currently there are only a few modern wifi chipsets readily available that work with free software systems. […]

what IT can learn from nature: (src) mostly US users affected. Big Business: Big Companies and Big Money can afford Big Staff to maintain and secure their products, but they also provide Big Infrastructure (AWS, Office) and thus a single […]

bc is a nice calculator that one can use under linux terminal. a good exercise: count from 0 to 255 and convert it to binary # install # debian/ubuntu apt install bc # fedora/redhat/centos yum install bc # run bc […]

Why is quantum computing important: optimization Update: Google claims to have reached quantum supremacy The tech giant unveiled its x-quantum computer chip Bristlecone in March 2018 (src: cnet) original nasa paper: https://drive.google.com/file/d/19lv8p1fB47z1pEZVlfDXhop082Lc-kdD/view book: https://deepai.org/machine-learning/researcher/eleanor-g-rieffel https://www.amazon.com/Quantum-Computing-Introduction-Engineering-Computation/dp/0262015064 Scott’s Supreme Quantum Supremacy FAQ! […]

Warum VoIP? Viele Anbieter von LTE z.B. bieten gar keine Festnetz-Telefonie an, sondern nur Internet. (das zum Teil (nicht günstiger) aber schneller (und schnurloser via Handy-Netz) als die Telekom (4G/LTE/UMTS)). D.h. man braucht dann noch einen weiteren Anbieter der die […]

it might sound strange… and even if it sucks, but if you are concerned about security, call me paranoid but: your company’s critical infrastructure SHALL NOT BE REACHABLE BY WIFI! (especially not if you are running a nuclear power plant, […]

the similarity is startling. They could be clones! (they probably are) except: D-Link is from Taiwan (still not China) and TP-Link is from Shenzen China bought recently 3x of the TP-Link 108 and can confirm they are doing a great […]

also roaming within the “(more or less)United States of Europe” (EU) is pretty scary endavor. If you travel across the EU and wish to use your home mobile phone number – you will NEVER know what this phone call or […]

servers/clients/computers/programs/services/webservers need accurate time… they usually get it from time servers that have an atomic clock attached to their USB port. (just guessing) ping time.google.com PING time.google.com (216.239.35.4) 56(84) bytes of data. 64 bytes from time2.google.com (216.239.35.4): icmp_seq=1 ttl=46 time=43.5 […]

the best about samba: thanks for samba, it provides users with a fast (of course depends also on harddisk speed) rock-solid no-limit-to-maximum-users file-server for maximum file-transfer-and-sharing-and-storage productivity (and they will USE that T: temp drive for EVERYTHING! prepare for TERRABYTES […]

IPv6: Introduction it’s the year 2019, roughly 14% of the web is running ipv6. you can watch real time statistics here: (i have no clue how accurate the data is, how they are generated) https://ipv6.he.net/v4ex/sidebar/? … but it seems there […]

firewall & pinguin: iptables where do thou go? it is said that when using “ip-sets” iptables and nftables achieve almost same performance (amounts of ips possible to block, without server becoming slow/unresponsive) Redhat and nftables on DDoS “so the only […]

sometimes you just want to listen to incoming traffic… not the noise that your machine generates: # checkout what mac your NIC has ip addr show; ifconfig -a; # filter it in wireshark not eth.addr==28:d2:XX:XX:XX:XX

CentOS8: ccze author not willing to maintain ccze. no ccze and not even lnav available. how to monitor all logs… https://dwaves.de/2017/06/15/linux-monitor-all-logs-in-real-time-d-follow-all-show-changes-to-log-files-under-varlog/ as i was wondering what combination of less -R with or without ccze would allow me to view log […]

Linux is pretty hardware independent, so most of the time you can just 1:1 clone/move harddisk to new machine and in 99% of cases it will just boot. make sure – target (new) machine’s harddisk is same or bigger size […]

basically the advanced version of PiHole. WARNING! THIS IS not a complete OPNSense / PFSense tutorial it is rather just to get started. right now, one is (still) using iptables without any gui. there seems to be a lot of […]

monitor (andoird) devices with bpf: https://www.socallinuxexpo.org/sites/default/files/presentations/bcc-scale.pdf so 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 […]

sad update: Peter Eckersley of Let’s Encrypt is Dead   may his soul find rest in the open source nirvana from earthly troubles… may the pain of his family and friends be overcome may let’s encrypt live on! Why: Do MAJOR […]

What devices lurk in the user’s network? What computers are online what offline? quick arp scan with netdiscover (manpage: netdiscover.man.txt scanning with nmap What services/ports in what versions are online/open? over poorly or not so poorly documented LANs the user-admin […]

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. […]

is it possible, to PC <-LAN-> AP <-Wifi-> AP <-> internet? With those TP-LINK routers, Yes it is! Why do other routers not have this “Wifi Bridge” (!) functionality? It is rather simple: How to created multiple Wifi AccessPoints connecting […]

on the one hand – software biodiversity is good – if one system get’s hacked or virus infiltrated – the other’s – if “different enough” probably stay unaffected. on the other hand – if config files or procedures or command […]

they essentially do the same – testing the router packages take to a certain destination – meassure time to travel. apt-get install iputils-tracepath; # to install tracepath on debian8, Tools to trace the network path to a remote host strangeness […]

per default debian is not configured to forward traffic. on server/router/gateway: ping yahoo.de; # make sure internet connection works ifconfig eth0:0 192.168.1.1 netmask 255.255.255.0 up; # add additional ip vim /etc/sysctl.conf # Uncomment the next line to enable packet forwarding […]

what service/program is using what port: https://dwaves.de/2015/06/16/linux-list-all-open-ports-and-listening-services/ IPTraf, Iftop, vnstat, bwm-ng, ifconfig -a graphical: gives you overall statistics the blue stuff on the left: iptraf manpage: iptraf-ng.man.txt you probably want to let it run in a screen session, in order […]

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 The CIDR number comes from the number of 1’s in the subnet mask when converted to binary. The common subnet mask 255.255.255.0 is 11111111.11111111.11111111.00000000 in binary. This adds up to 24 1’s, or /24 (pronounced […]