UNIVERSITY OF COLOMBO

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UNIVERSITY OF COLOMBO SCHOOL OF
COMPUTING
IT5501 Systems Network Administration
DEGREE OF BACHELOR OF INFORMATION TECHNOLOGY
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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.
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Windows 2000 File Systems
FAT16 FAT32 NTFSv5
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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.
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FAT16 Default Cluster Sizes
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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.
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FAT 32 Default Cluster Sizes
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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.
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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.
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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 /.

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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.

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Host Management (Unix)

• File access control
• To restrict privilege to files on the FS
• 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)

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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

• --x 5 r-w
• -w- 6 rw-
• -wx 7 rwx
• r--

owner
Type of file
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Network Management
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IP Addressing

• IP address classes A, B, C, ..

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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.

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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.

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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.
Subnet mask 11111111.11111111.11111111.11111000 i
e., 255.255.255.248 or we can write it as
196.200.150.0 / 29
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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.
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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 _at_ 62 hosts
• SM 255.255.255.224 /27 ? 6 subnets _at_ 30 hosts
• SM 255.255.255.240 /28 ?14 subnets _at_ 14 hosts
• SM 255.255.255.248 /29 ?30 subnets _at_ 6 hosts SM
  255.255.255.252 /30 ?62 subnets _at_ 2 hosts

When do we need to use different subnet masks?
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Variable Length Subnet Masking (VLSM)
E1
E2
R
R
Leased Line
Colombo Head Office 50 hosts
Kandy Branch Office 25 hosts
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Variable Length Subnet Masking (VLSM)
E1
E2
R
R
Subnet 2
Colombo Head Office 50 hosts
Kandy Branch Office 25 hosts
Subnet 3
Subnet 1
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Variable Length Subnet Masking (VLSM)
E1
E2
1
1
1
1
R
R
50
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Colombo Head Office 50 hosts
Kandy Branch Office 25 hosts
No of IP Addresses Required 50251111 79
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Variable Length Subnet Masking (VLSM)
For the serial link needs only 2 IPs
SM 255.255.255.252IPs 200.10.15.5 /30
and 200.10.15.6 /30 For Kandy subnet needs 26
IPs SM 255.255.255.224IPs
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
255.255.255.192IPs 200.10.15.65 /26 ? E1
and 200.10.15.66 /26 to 200.10.15.115 /26 (m/c)
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Variable Length Subnet Masking (VLSM)
E1
E2
200.10.15.5/30
200.10.15.6/30
R
R
200.10.15.33/27
200.10.15.65/26
Colombo Head Office 50 hosts
Kandy Branch Office 25 hosts
200.10.15.66 200.10.15.115/26
200.10.15.34 200.10.15.58 /27
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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

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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 (link-state)BGP, EGP
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Further Information

• www.bit.lk
• Detailed Syllabus Topic Objectives
• Information ? Course Structure ?
• Semester 5
• Queries
• sna_at_ucsc.cmb.ac.lk