Author Archives: cisco-linux

IT technical jargon

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Some IT technician words can make confuse and provide misunderstanding therefore please read the list below to be familiar with these expressions:

  • Adware – if you have this type of programme loaded onto your computer, you will start getting pop-ups even when you’re not online! If you click on the pop-up it will take you to a specific web site where you will be encouraged to enter your credit card details. Typically these are scames, so our advice is to never buy anything using pop-ups that just appear on your screen.

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Linux terminal keyboard shortcuts

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A few keyboard short-cuts to use working in Linux terminal either in a text mode or desktop X session:

  • [Ctrl] + [Alt] + [Fn] = it switches screens.
    [Ctrl]+[Alt] + [F1] through [F6] are text-mode shell prompt screens and [F7] is the graphical desktop screen.
  • [Ctrl] + [Alt] + [Delete] = When is used in graphic desktop session it shuts down Cent OS, Red Hat and should work similar with any other Linux distribution. To use only when the normal shutdown procedure does not work, this short-cut will display the desktop logout screen that allow you to logout, reboot, or shut down.

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IPv4 special addresses of Internet Protocol version 4

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IP is the most commonly used communication protocol suite in Internet. Most of us know that this 32bit IP address range has been divided on public and private addresses – what we have at home (private) and what is reachable on Internet (public). But underneath there are more IP pools and not everyone knows that in the IP world there are special address ranges used to cover extra tasks and services provided for us like stream video, routing updates and time updates.

During the exhaustion 32bit ver4 IP pool have changed and the modern division approved by Cisco and Internet Organisations (IEEE and IANA) is the current standard shown below. Continue reading →

Hide your IP using ssh socks proxy

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Socks proxy using SSH

Tunnelling over our Internet link it sounds already exiting, isn’t it?. But how difficult is it? Do we need any complex and sophisticated configuration of hardware and software? Hmm.. it is not necessary even to involve ipsec or ssl stack to create VPN. SOCKS is built in to OpenSSH so it’s trivial to run SOCKS proxy server with ssh client running with option -D. This option configures SSH client to listen on your local Linux box on specified by us tcp port. Then  we will use SOCKS5 proxy configuration built into most of Internet browsers to connect to.

ssh-socks-proxy
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Cisco enable http server

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Follow these steps to enable https secure web configuration on your router or switch:

#conf t
 username tech privilege 15 secret 0 userpassword '<-- create user tech with the highest privileges'
 ip http server '<-- enable http access'
 ip http access-class 23
 ip http authentication local '<-- enable local authentication'
 ip http secure-server
 ip http timeout-policy idle 60 life 86400 requests 10000

VLANs on Cisco switch or EtherSwitch card

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VLANs

VLANs concept is very well known to separate network traffic on single switch to increase security. This allows more clearer network design minimizing needs for an additional hardware to deployed. The below example has been tested on Cisco 1900 series router eqquipped with EHWIC-4ESG-P EtherSwitch card. This configuration supports up to 16 VLANs but higher end devices can support up to 4096 VLANs. Please refer to your device documentation for more details. Continue reading →