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About Mahendra Singh
Expertise
I would like to answer questions related following: 1. IT Services such as Help desk, Hardware/Software/Programming for internet. 2. Business in Europe. 3. User/Demographic information. 4. Internet Programming languages such as ASP/PHP. 5. Servers : IIS, WebLogic. 6. Research based questions such as "What is the common use of internet in Europe and demographs"

Experience
I answer questions on various European sites which are Business/Demographics and other issues related to EU.

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You are here: Experts > Internet/Online > Internet Appliances > Internet Appliances > How to distinguish 127.0.0.1 vs WAN ip address vs 0.0.0.0

Topic: Internet Appliances

Expert: Mahendra Singh
Date: 7/2/2007
Subject: How to distinguish 127.0.0.1 vs WAN ip address vs 0.0.0.0

Question
I feel confused and do not know how to use them correctly , when , why ...
I have an image captured from my Kaspersky firewall , please help me understand how it works , the chain packets are passed .
http://img116.imageshack.us/my.php?image=kasel4.jpg

And This firewall config also
http://img211.imageshack.us/my.php?image=firewalltt6.jpg

Thank you very much !

Answer
Hi Martin,

Every WAN device have two interfaces. one for internal and second for external.

Internal is supposed to have 127.0.0.0 something. External should have 53.56.78.89 like ip. 0.0.0.0 is defined for access lists and routing lists. 0.0.0.0 means in networking terms "ANY" . for example if you have access list or routing like this 0.0.0.0 -> 0.0.0.0 , it means allow from any interface to any interface. If you have something like this 127.0.0.0 -> 45.56.89.0 means that allow traffic coming from 127.x.x.x to go from 45.x.x.x ip .

For IP addresses you may read this short doc at
http://www.3com.com/other/pdfs/infra/corpinfo/en_US/501302.pdf

and a good resource at
http://www.unet.univie.ac.at/aix/aixbman/commadmn/tcp_address.htm

I hope it helps.

Thanks
Mahendra Singh

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