Re: Antw: Re: Firewalling a cable modem

Michael Kamp wrote:

I am just a beginner in security. What security feature is added by NAT?
As fas as I know, the router looks up the mac address of my pc and sends
the incoming packets to my network card.

But what's added by NAT? And even more, if NAT adds something, why does
it help only small home networks?

NAT is all you need for a small home network. SPI would be the next step
up in security.

NAT

Short for Network Address Translation, an Internet standard that enables
a local-area network (LAN) to use one set of IP addresses for internal
traffic and a second set of addresses for external traffic. A NAT box
located where the LAN meets the Internet makes all necessary IP address
translations.

NAT serves three main purposes:

# Provides a type of firewall by hiding internal IP addresses
# Enables a company to use more internal IP addresses. Since they're used
internally only, there's no possibility of conflict with IP addresses
used by other companies and organizations.
# Allows a company to combine multiple ISDN connections into a single
Internet connection.

Try here or Google for more info on firewalls :

http://www.pcmag.com/encyclopedia_term/0,2542,t=firewall&i=43218,00.asp
.

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