Network | FyhTech

Fairphone2 has a problem with 2 sim cards

Today I inserted another sim card in my fairphone 2. I want to use LTE with this card, but I wasn't able to configure 4G/3G/2G. 2G was selected and the button was disabled. So I just had 2G. The other card worked as expected and I was able to choose 4G/3G/2G. This bothered me the whole day.

In the evening I figured out how to fix the problem:

Simple WebApp-Stress-Tool

Simulty is a very simple webapp-stress-tool. It reads random urls from a file and executes multiple get-requests simultaneously to them.

Setup LXC-Container in Debian Jessie

LXC-Containers are very useful. They are more leightweight than virtual machines and not as static as docker-containers. That's why I like them especially for my server environments. In this article I will show a very basic setup of LXC-Containers on Debian Jessie.

Shorewall: setup Geo-IP filtering

shorewall - iptables made easy

Sometimes it is neccessary to filter packets based on their geo-ip location. Shorewall can make use of the xt_geoip-module for iptables. In this article I will explain how to setup this module on Debian.

Tcpdump: capturing ipv6-packets only


tcpdump -i eth0  ip6

Filetransfer using netcat

It's quite easy to share files using netcat.

Serve a file on a listening port:


cat myfile.txt | nc -l -p 1337

Connect to this port and download file:


netcat SERVERIP 1337 > myfile.txt

Tcpdump: capturing packets with specific tcpflags

Let's catpure for example only tcp-packets with syn or ack-flag set:

tcpdump "tcp[tcpflags] & (tcp-syn|tcp-ack) != 0"

Guacamole: A clientless remote desktop gateway using HTML5

Guacamole is a clientless remote desktop gateway using HTML5. It supports the following backends: VNC, RDP, SSH and Telnet. It really looks like a promising project to me

Static arp-cache on dhcp-servers

We can use static ARP entries on hosts or routers to reduce ARP-traffic or to prevent ARP-spoofing. For such entries we need pairs of MAC-addresses and IP-addresses. The same information we also need for static DHCP-entries on a DHCP-server. Why not combine?

Route to nowhere - Blocking attackers using Nullroutes

If someone attacks a linux-system, most administrator would block the ip-address of the attacker using iptables-rules. But there is another method to block the address of an attacker: nullroutes. A Nullroute simply directs to nowhere.