software firewall vs router

i have just installed a router. What are the basic differences between it and software firewalls. What functions does as router do as opposed to those of a software firewall.

The basic function of small routers are to perform Network Address Translation and to route traffic. That is your internal network has a set of IP addresses – if it is in your home or small office they are probably private IP addresses. {non routable} Say you have 5 computers in your home/office and 1 connection to the internet. You are going to have 1 IP address which is what your ISP gives you and anyone in the world can see. You are going to have 5 IP addresses on your 5 computers and an additional address on your internal port of your router. Your external port on your router has the IP your ISP gave you.
Lets say you are connecting to AO from one of the PCs on one of your 5 hypothetical computers:
You enter the URL and hit enter. The router “routes” traffic from the internal computer through the gateway address {internal port on the router} to the external port of the router and then on to the internet address you are connecting to. When the page is found it is returned to the external port of your router. The router remembers which computer requested the page and forwards the page to that computer.

Depending on the type of router will dictate what “firewall” qualities it can perform. Most Cisco as well as Linksys routers can be set to only allow return traffic through the ports, that is anything you request will be returned but a scan initiated externally will not. On the Cisco routers you can also enter ACL {Access control lists} of Ips you wish to block.


With everything advancing there is a lot of overlap of what components do, whereas “back in the day” each device did its job and had to work in conjunction with other parts.

A firewall is basically a filter that looks at each packet of info that goes through it and applies a set of rules you define. Kind of like the inbox assistant you can set on Outlook for incoming e-mails.

Check this link for info on Firewall info:
http://homepage.ntlworld.com/susan.todd3/basics.htm
Check this link for more info on Routing basics:
http://www.incoma.ru/protocols/tcp_ip.html

They both have graphic illustrations that should help.

Some of this can get pretty complicated, but this should get you started.

Also, a router alows you to do loads balancing and backup routing if your main connection goes down.

for example if u have a T1 + dsl + isdn connections, your main connection is the T1 and if it goes down, the dsl picks up automatically trough and if it fails too the dsl picks up and finally the isdn will. (this is not a reallistic scenario btw)

The router also allows you to specify load balancing wich in the preceeding case would bring both b cannals of the isdn is the bw required was greater then 64k

Also, the router can be used to specify routing protocol in big private networks there are several protocol used such as ( from very small to humengous size): rip, igrp, eigrp, ospf, is is , bgp and there are many others. the advantages of having routing protocols is that u don't have to define each route staiscally, the routers advertise each of the neworks he is conected to ( depands on config and on protocol used ..)


The main difference is that routers are always harware and firewall are aminly soft ....