The Diary of a SysAdmin

I think it is better to tell the difference of Subnet Mask and Variable Length Subnet Mask(VLSM) at the beginning. As I discuss in earlier article Subnet Mask is there to split one IP address into several IP’s which can use in difference LAN’s. But the question is it limit the number of accessible hosts(computers) in each LAN.  Let takes the previous example,  192.168.5.0/26 (LAN A) can only have 62 (2^6 -2) computers(hosts). But Imagine that we need to keep 100 computers in LAB A? Now I think you can understand how Subnet Mask is questioned. The answer is Variable Length Subnet Mask. I try to discuss how we use VLSM in practice in this article. I rearrange the previous example as following. ISP given address -> 192.168.5.0 /24 LAN A -> 100  (lets think LAN A need 100 computers). LAN B ->50 LAN C -> 50 LAN D ->50 Let see how we solve this problem. 192.168.5.0 /24 is the given IP and we take one bit from host side of that IP. We can define two different IP’s b

Imagine that you need to make four different networks(LAN’s). Then you ask form ISP(Internet Service Provider) to four different IP’s. But each of network has less than 20 computers. So ISP will say we cannot give four IP’s and we give you one IP and Split it into four difference networks. Let see how we done it. ISP given network address: 192.168.5.0 255.255.255.0                                                                                                                                  The number of networks that we have : 4 (2^2) 192.168.5. 00 000000        (we take two bits from available host’s bits because we need four different networks).       0     0     0   0   0  0  0   0        (consider last 8 bits) 128  64  32 16  8  4  2   1 00  -> 192.168.5.0       LAN A                                01 -> 192.168.5.64      LAN B 10 ->192.168.5.128     LAN C 11 ->192.168.5.192      LAN D LAN Name Network Address Broadcast Address Host’s IP Range

As I mention in earlier article network address will give when we make all host side bits zero. The main difference between class full and class less IP addressing is there is no standard bit position to divide network and host side in class less IP. But we had to tell what is the point that network and host side divide in this case. That is why sub net mask address comes to seen. Subnet mask address is also 32 bit binary number. The sub net mask address will give when all network side bits makes 1(one ‘s) and all host side bits makes 0(zero). I think you can take better idea by looking  following e.g. e.g. 1 IP Addr: 192.168.1.1                                        11000000.10101000.00000001 .00000001 Sub net mask: 255.255.255.0                             11111111.11111111.11111111 .00000000 We can write both IP and sub net mask or can write like this, 192.168.1.1/24. Number of network side bits are written as “/n “ after the IP.    e.g.2 Let say 192.168.1.1/26 and a

I try to discuss in brief some key terms in IP Addressing in networking. 1.        Class full IP Addressing 2.        Class less IP addressing In network computer needs to identify their destination and host computer  among others, to communicate each other. So it used 32 bit binary number for that, and split it into equal 4 parts and convert it to decimal for easy use. E.g   11000000.10100000.00000001.00000001          192.168.1.1  To identify one computer from large network is not easy by concerning one by one digit. So that there are two things within on IP. Network address and Host(computer or any device) address. This process like this, when we post a letter it address look like this,(No 35,Reid Avenue,Colombo 07).If we post that letter from galle the post office(galle) just looks the colombo and sends it to the colombo.Rest of the parts of address (road and number) looks by colombo post office.The IP address also looks like that.Router look the network address and try to send