subnet masking

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hi gents,

i am new on ICND1 can you help me on subnet masking? i can easely understand what is IP adress but i am not sure about mask.

what is this mask for?
what type of problems can solve by it?

 

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You may find these videos helpful. See section 1.3 – IP Addressing
Professor Messer’s CompTIA N10-005 Network+ Training | Professor Messer - CompTIA A+, Network+, Security+, Linux, Microsoft Technology Training

 

Subnetting is mainly used for conservation and management of networks. It would be difficult for me to explain the process of how to subnet, I strongly advise watching the 3 cbt nuggets subnetting videos by Jeremy.

Why?
So there are many reasons for subnetting, mainly the use is for conservation and management of IP addresses. Often in a corporate environment you want to allocate a specific range of addresses for things such as firewalls / routers / proxies etc... And to have your users on their workstations to have lets say have 50 addresses from the same range.

Assume you only have the network 192.168.1.0 255.255.255.0, to play with. You need to reserve 10 IP's for your networking equipment 50 IP's for your users workstations and 50 IP's for each users VoIP phone. You can split the network into logical sections by manipulating the subnet mask.

The reason we would do this is to keep the network organised and manageable. You can also limit user access to certain resources by subnetting. For example if you have the following range set for workstations 192.168.1.0 / 26 (255.255.255.192) This gives you 62 usable addresses, that will you can set access lists / firewall policies around on what those IP address can access. Also if you are troubleshooting network problems, or looking at packet captures and see the address 192.168.1.24 communicating you can say, well I know there is a range of IP addresses that run from 192.168.1.0 to 192.168.1.64. There for I know the address is coming from a host in that network range. OK I can now see the source of the problem is with workstation (x).

Hope this helps you understand the need for subnetting and check out the videos from CCENT cbtnuggets, they will help alot.

 

Hey, I can see this has been answered by some pointers to some real good resources. In my view Messer is the absolute don for online training - I owe him my 70-680 - but I've had a few students who just didn't get along with his way of explaining stuff. Everyone's different, so it never hurts to have access to a few answers, and here's my own attempt to answer a similar in another thread. Feel free to have a look, see if it helps...