Month: July 2012

Transparent Firewalls

A firewall in terms of traditional network configurations serves as a default gateway for hosts connecting to one of its secured subnets. A transparent firewall acts like a “stealth firewall” and it is actually a Layer 2 firewall. In order to implement this, the connection of the security equipment is made to same network on both the internal and external ports. However, there is a separate VLAN for each interface.

Now let’s discuss the characteristics of transparent firewall mode:

  • Transparent firewall mode supports outside interface and an inside interface.
  • The best thing about transparent firewall mode is that it can run in both the single and multiple context modes.
  • Instead of routing table lookups the MAC lookups are performed.

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How does Firewall defend our Network?


We all are familiar with the term ‘firewall’ but majority of us don’t know the source of its origination. It is actually a terminology used for describing a part of automobile that separated the automobile’s interior from the compartment of engine. In the world of network this term is used metaphorically to show the way internal networks are separated from the hazards of external world. With the help of firewalls the networks are divided into various physical networks and as a result of this the occurrence of potential damages can be controlled otherwise these damages can spread to different subnets.

This works in the same way as the original firewalls worked to stop the spreading of a fire.

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MIME – Multipurpose Internet Mail Extensions

MIMEInternet standard MIME is able to extend the e-mail format for the purpose to support the following things as text, non-text attachment, a message organization with manifold parts and non-ASCII header information. The existence of MIME protocol has become very important because SMTP as basic e-mail transmission protocol can support only 7-bit of ASCII characters set. But MIME as Presentation layer protocol can hold up 8-bit binary content by describing the ways of sending certain types of data via an electronic mail.

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