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UNIVERSITY OF COLOMBO SCHOOL OF COMPUTING IT5501 Systems & Network Administration DEGREE OF BACHELOR OF INFORMATION TECHNOLOGY Host Management Files and file systems are the very basis of what system administration is about. Almost every task in host administration or network configuration involves making changes to files. Windows 2000 File Systems FAT16 FAT32 NTFSv5 FAT16 When a FAT16 volume is formatted the size of the volume determines the default cluster size. The cluster number cannot exceed a value that can be represented by 16bits and must be a power of 2. FAT16 Default Cluster Sizes Volume Size (MB) 0 – 32 33 – 64 65 – 128 129 – 256 257 – 512 513 - 1024 1025 – 2048 2049 - 4096 Cluster Size 512 bytes 1KB 2KB 4KB 8KB 16KB 32KB 54KB FAT32 Microsoft introduced FAT32 with Windows 95. They implemented FAT32 with few changes to the existing FAT16 architecture in order to remain compatible. Windows 2000 will format FAT32 volumes only up to 32GB in size. One of the significant changes was the use of 4 bytes to store cluster values as opposed to 2 bytes in FAT16. FAT 32 Default Cluster Sizes Volume Size Less than 8 GB Default cluster Size 4KB Between 8 and 16GB 8KB Between 16 and 32GB Greater than 32GB 16KB 32KB In Windows 2000 to see the cluster size of a volume we have to get the Windows 2000 Defragmentation report. Otherwise on the command prompt CHKDSK command can be used. NTFS NTFS is used solely by Windows NT and Windows 2000. It uses relational database, transaction processing and object technologies to provide such features as data security and file system reliability. File system recovery, large storage media and support for object oriented applications are the other features. Host Management (Unix) Unix has a hierarchical file system – directories and sub-directories form a tree. Based on a system of inodes, in which every file has an index entry. inode is a pointer to the actual disk blocks which are associated with the file. Top or the start of the Unix file tree is called the root file system and is denoted by “/”. Host Management (Unix) File locations will differ for different versions of Unix, but the basic features are the same. /bin - executable programs /usr - application s/w lives here + basic libs /sbin - statically linked system binaries /etc - misc. programs + config files /dev - place where all logical devices are in /var - for spooling + logging /home- each user has a separate login directory to keep their file. Host Management (Unix) File access control 1. To restrict privilege to files on the FS 2. To create the illusion of a virtual host for every logged-on user. In Unix a files contents are classified by “magic nos” – kept in the file inode E.g.. A file belongs to user Saman is owned by that person. Saman can decide whether or not other users can read, write or execute the file by setting the “protection bits”. (chmod) Host Management (Unix) There are 16 protection bits for a Unix file, but only 12 of them can be changed by users. drw-r-x--x 2 root wheel 2345 Oct 28 myfile Anyone (world) group owner Type of file 1 --x 5 2 -w- 6 rw- 3 -wx 7 4 r-- r-w rwx Network Management IP Addressing IP address classes: A, B, C, ….. Subnetting • A subnet is a physical segment in a TCP/IP environment that uses IP addresses derived from a single network ID. • By partitioning the bits in the host ID into two parts, Subnet ID and the Host ID, a single Network Address can be used to uniquely define a set of subnets. • The number of hosts available for the Network address will be distributed among the subnets. Subnet Mask and IP • A subnet mask is a 32-bit address used to block or “mask” a portion of the IP address to distinguish the network ID from the host ID. • Each host on a TCP/IP network requires a subnet mask, either a default subnet mask or a custom subnet mask. • A default subnet mask is used on TCP/IP networks that are not divided into subnets. • In the subnet mask, all bits that correspond to the network ID are set to 1. All bits that correspond to the host ID are set to 0. Subnetting Example Divide 196.200.150.0 into 15 sub-networks. Needs to borrow 5-bits from the host part to have 15 sub -networks. 196 200 150 5-bits 3-bits Subnet mask: 11111111.11111111.11111111.11111000 ie., 255.255.255.248 or we can write it as 196.200.150.0 / 29 Variable Length Subnet Masking (VLSM) is the process by which we take a major network address and use different subnet masks at different points. If we have to keep the subnet mask the same we encounter severe problems concerning addressing space. Variable Length Subnet Masking (VLSM) Consider a class “C” IP address : 200.10.15.x Default (subnet) mask (SM): 255.255.255.0 SM 255.255.255.192 /26 2 subnets @ 62 hosts SM 255.255.255.224 /27 6 subnets @ 30 hosts SM 255.255.255.240 /28 14 subnets @ 14 hosts SM 255.255.255.248 /29 30 subnets @ 6 hosts SM 255.255.255.252 /30 62 subnets @ 2 hosts When do we need to use different subnet masks? Variable Length Subnet Masking (VLSM) E1 E2 R R Leased Line Colombo Head Office 50 hosts Kandy Branch Office 25 hosts Variable Length Subnet Masking (VLSM) E1 E2 R R Colombo Head Office 50 hosts Subnet 1 Subnet 2 Kandy Branch Office 25 hosts Subnet 3 Variable Length Subnet Masking (VLSM) E1 E2 1 50 Colombo Head Office 50 hosts R 1 1 R 1 25 Kandy Branch Office 25 hosts No of IP Addresses Required 50+25+1+1+1+1 = 79 Variable Length Subnet Masking (VLSM) For the serial link – needs only 2 IPs SM – 255.255.255.252 IPs – 200.10.15.5 /30 and 200.10.15.6 /30 For Kandy subnet – needs 26 IPs SM – 255.255.255.224 IPs – 200.10.15.33 /27 E2 and 200.10.15.34 /27 to 200.10.15.58 /27 (m/c) For Colombo subnet – needs 51 IPs SM – 255.255.255.192 IPs – 200.10.15.65 /26 E1 and 200.10.15.66 /26 to 200.10.15.115 /26 (m/c) Variable Length Subnet Masking (VLSM) E1 E2 R Colombo Head Office 50 hosts 200.10.15.66 – 200.10.15.115/26 R Kandy Branch Office 25 hosts 200.10.15.34 – 200.10.15.58 /27 Variable Length Subnet Masking (VLSM) When can VLSM be used? VLSM can only be used with a classless routing protocol. Classless routing protocols: RIP Version 2 OSPF Routing Protocols All routing protocols perform the same basic function – determine the best route to each destination and distribute these info among the systems. Routing protocols: interior (within AS) & exterior (between ASs) RIP (hop count), Hello (delay), OSPF (linkstate) BGP, EGP Further Information www.bit.lk • Detailed Syllabus & Topic Objectives Information Course Structure Semester 5 • Queries [email protected]