A firewall is a part of a computer network that is designed to block unauthorized access while permitting authorized communications. It is a device or set of devices which is configured to permit or deny computer based application upon a set of rules and other criteria.
In firewall all interface classification on the basis of security level of ZONE .
Three type of zones in firewall INSIDE ,OUTSIDE ,DMZ.
INSIDE :-security level is 100 by default (Trusted Zone) .All lan network join in a INSIDE network zone.
OUTSIDE:-security level is 0 by default (Untrusted Zone ) .Internet zone is also know as Untrusted zone .
DMZ :-in between 1-99 security level define according to company policy by default all company use 50 security level in DMZ .All server connected in DMZ network zone .
Type of Firewall:-
- Packet filter 2.Application gateway 3.Circuit level gateway 4.Proxy server
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