what is subnet mask?

Question

why is it always 255.255.255.0?
why is the router's internal ip address always 192.168.254.254?
Is the DNS the same as the ISP? if not, what / where is it?
please help i'm not clear with these concepts.

Answer 1

Well, in simple terms a subnet mask is a way of telling your computer or router what network addresses it can consider local and which are remote. Subnetting an IP network allows a single large network to be broken down into what appear (logically) to be several smaller ones. Most home routers are set to 255.255.255.0 which allows 256 addresses. Since you said your system uses 192.168.254.254 as the router your "Local" IP ranges are 192.168.254.0 - 192.168.254.255. (You can use 254 for computers as two of those are reserved for the allocations 0 and 255.) What the subnet mask tells the system is that those addresses are local and any other IP address will be on the "wide area/internet" side of the router!

If you want to see how that plays out, play with the subnet calculator at http://www.subnet-calculator.com/ or you can learn all about it at

http://www.learntosubnet.com/



Most home routers use 192.168.0.1 or 192.168.1.1 as the routers address. (You can set this in the router under the DHCP section) This is a LOCAL address that is assigned by the owner (you) to the router. Many manufacturers just pick one. In your case they used 192.168.254.254 as the "default" which you can change. These are your own networks "private" IPs. You can see a list of IP ranges that are assigned for "private" use here. http://www.duxcw.com/faq/network/privip.htm





The DNS is used for "number to name" lookup called Domain Name Service. Servers are usually setup by the ISP specifically to deliver that lookup ability for you. What is does is convert names like "yahoo.com" to and IP address so your computer knows where to go to find yahoo. All the internet is addressed by IP addresses - with a name lookup to cross to that address.. Like a big phone book! You can use your ISP's assigned addresses or you can use any of the "Public" dns servers to have DNS services working on your system! In home networks, the router usually gets this information automatically from the ISP and then you use the router as the DNS server! Here is a list of "Public - available to anyone" DNS servers http://www.tech-faq.com/public-dns-servers.shtml



Hope that helps a little. These networking concepts are the basis for all networking. People spend hours/months/years really to get the concepts understood.

Answer 2

Ip subnet mask calculator:

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Answer 3

the isp issues you an ip

the router acts as a traffic cop directing traffic

with nat - it creates an internal network - subdividing the ip from the isp into its own network

dns - dynamic naming service

everything on the internet goes back to numbers

for convenience dynamic naming computers ( dns) are computers which translate those numbers into letters for you - its for convenience of users- if you remembered the numbers for say google if you typed those you would be directed to the site

usually people use the dns of the isp - you do not have to any will do

try open dns to speed your internet browsing speeds



http://www.opendns.com/



about the subnet mask

It was best described to me as blinders

For traffic that is directed internally in the network

- say you use msn messenger to transfer large files between computers on your network - handshake is done on the net , files are transferred though between the 2 computers within your home network at high speed - having those numbers of the subnet mask makes it quicker and easier to route within the router home network



lastly the dns is issued by the router by the dhcf service

Some of the time in setup you may turn it off

the router then acts as a switch only



networking people are the prima donnas of the computer world

they will not tell you much - too self important and busy

older networking books will tell and explain such things



useful site http://portforward.com/routers.htm

Answer 4

I agree with Tracy L in the fact that it can take some people hours/days/months/years, to understand these while others just get it. the subnet is just a way of breaking things down, telling your computer the range of ips to accept. Like Tracy stated yours will range from 0-255.

Answer 5

well...start with the network itself , it assigns your IP address in your routers case it has two ip addresses, the one your Internet service provider (ISP) and one to denote it's address in your network (usually 192.168.1.1 but can be different) since you are connecting to the network (the internet) through your router you have a home network that connects to the internet through your router. your computer doesn't know when it is connected to the router so it doesn't know it needs two IP addresses to get out to the internet that is where your dns gateway comes in. the dns gateway is the same as your routers IP address, it tells your computer to ask the router for permission basically. the subnet mask is almost never used in a home network so it is always 255.255.255.0 . the subnet mask is used in very large networks to seperate that network into smaller networks that all can all connect to a single source but not each other. each set of three numbers is an octet allowing for an astronomical number of smaller networks.

Answer 6

Here are some sites to learn and practice subnetting:



http://easysubnet.com

http://www.subnettingquestions.com

Answer 7

check this link for complete infos about subnet mask.

http://www.topwebhosts.org/tools/netmask.php

Answer 8

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