Firewall Part -1

Dear Friends ,in our previous threat we looked about securing of data i.e privilege classification, securing of data in stored environment, securing of data while in communication.

Today let us look about function and evaluation of firewall . Firewall in network terms connecting private secure network with secure public network to outside world through a secured environment. Secondly it has great impact on controlling IPV4 public IP addresses.before we are going into deep about firewall technology. Let us have a basic understanding of IP addresses and ports  

IP address : its an a internet  protocol address assigned for all networking devices, devices will communicate with their assigned  ip address. It's a 32-bit address . As per IANA ( Internet Assigned Numbers Authority) has segregated public and private IP addresses.

Public IP address: Public ip addresses are globally assigned unique IP addresses used for networking devices to communicate with global network.

Private IP address: Private IP address are assigned internally to an organisation, but when its need to communicate globally its needs public IP address.  Below are ranges of IP address and its classes instructed by IANA to use as private  IP ranges.

RFC1918 name	IP address range	number of addresses
24-bit block	10.0.0.0 – 10.255.255.255	16,777,216
20-bit block	172.16.0.0 – 172.31.255.255	1,048,576
16-bit block	192.168.0.0 – 192.168.255.255	65,536

Due to the lack availability of unique public IPV4 addresses leads to the development of IPV6, due to the lack availability of public ranges leads to formation of NAT/ PAT concepts .

What is nat , as all we know all the devices need an unique public ip address to communicate with outside globally, how about private IP ranges here the NAT concept is raised Network address Translation means Translating private IP into public IP address. This translation part will be done firewall and what about a group of private IP addresses ? this can be done by translating using single public IP with port address  , it's known as port address translation PAT.

Now lets come back to our firewall discussion, as we discussed previously firewall will act as inter-mediator with private internal network with communicating with external global network with IANA assigned public IP addresses .

Thus your internal network ranges will never know to the outsider, it's a type of securing our internal networks.

Default rule for firewall is internal users can able to access outside network without any restricted, whereas the restricted outside users only can able to access our Internal network, with the certain rules for allowing and denying, commonly it's referred as ACL it will be deny by default .

Due to advanced in technology, firewall also underwent serious of changes with the added functionality. Let us discuss about generation growth of firewall technology on next threat.