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Cloud Computing – Mind your WAN connection!

The last couple of years i’ve been involved in some projects regarding Cloud Computing and had to face with performance issues at some of these clients. The situations were almost identical; – Customer switched from client-server to Cloud Computing (Citrix or something similar) – Existing internet configuration is used and/or extended – All application- and ...

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Cisco IOS – Enabling netflow

I’ve  been using Netflow to monitor network traffic since beginning of this year and still i’m a big fan. Netflow allowes you to really dig in the actual network traffic that is generated by servers (or services) and let’s you investigate traffic that should be blocked. Configuring a Cisco to export netflow statistics to a ...

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Suse – Zypper download only option

On Suse there are both Yast and Zypper but sometimes i need the option to download source packages to customize them for install. [code]zypper -l -y update –download-only[/code]

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NFDump – Librrd issues

I’ve had a lot of issues when installing NFDump on a new Wheezy (Debian) system. I solved it after hours of pain. The error i had: [code]configure: error: Can not link librrd. Please specify –with-rrdpath=.. or[/code] So i added the path to my lib folder and got: [code]configure: error: C preprocessor “/lib/cpp” fails sanity check[/coe] ...

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Cross compiling fontconfig with xml2

Trying to compile fontconfig on a suse box i kept getting errors about libxml2 not beeing found. I knew this had something to do with the include path’s but trying to set them manually didn’t work. This fixed by problem: [code]export LIBXML2_CFLAGS=$(xml2-config –cflags) export LIBXML2_LIBS=$(xml2-config –libs)[/code] Now just run [code]./configure; make; make install[/code] You should ...

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IPtables Firewall – Rules testing

Did you ever configure a firewall and locked yourself out? Then you might like these commands to test IPTables configuration for a few seconds and then killing the process. [code]iptables restart; sleep 20; iptables stop[/code] This way you have 20 seconds to see if the rules are in order; if not you just wait until ...

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Cisco: Filtering based on AS numbers

I am currently trying to lock down a firewall with only a few accept rules for actual servers/traffic. Since there is some connectivity to the internet needed (like Windows updates and such) we need to filter this with access-lists. With these access-lists i simply create a few ‘ALLOW’ rules for actual traffic and a ‘REJECT’ ...

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Port forwarding through SSH/Putty

I often exchange data between work and home. This can be anything, from local websites that i develop at home or filetransfers that i dont want anybody to know about ;-). To maintain security i have a firewall at both my office and at home so i needed to find a way without creating specific ...

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XenServer – VDI not availible

When starting a VM we received the error ‘the vdi is not availible’ and the virtual machine refused to boot. Usually this error would mean a migration between physical servers went wrong or one of these servers went down unexpected. Since every host has a lock on the vm’s that are running on it you ...

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Linux – Honey Pot

Directly quoted from Wikipedia; In computer terminology, a honeypot is a trap set to detect, deflect, or in some manner counteract attempts at unauthorized use of information systems. Generally it consists of a computer, data, or a network site that appears to be part of a network, but is actually isolated and monitored, and which ...

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