1

Review For Exam 2

(Week 8, Wednesday 3/1/2006)

© Abdou Illia, Spring 2006

2

IP Subnetting

3

Structure of IP addresses

Network Part (n)Local Part (h)

Class A nnnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh 10.0.0.1 – 126.255.255.255

Class B nnnnnnnn.nnnnnnnn.hhhhhhhh.hhhhhhhh 128.0.0.1 – 191.255.255.255

Class C nnnnnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh 192.0.0.1 – 223.255.255.255

Sgmt. part Host part

4

Reserved IP addresses

Class Range

A 10.0.0.0 – 10.255.255.255

B 172.16.0.0 – 172.31.255.255

C 192.168.0.0 – 192.168.255.255

IP addresses reserved for private use.

Address Use

255.255.255.255

Example: 10.255.255.255

Local broadcast to LAN computers

Broadcast to network 10.0.0.0/8

127.0.0.1 Loopback address (for self addressing)

0.0.0.0 Prohibited

169.254.x.x Automatic Private IP Addressing

Special IP addresses.

5

Structure of IP addresses

The division between Network part, Segment part, and Host part is determined by a computer or a router by using a network mask.

Network PartSegment

PartHostPart

6

Network mask A 32 bit number, just like an IP address,

where all bits in the Network Part and the Segment Part are set to 1, and all bits in the Host Part are set to 0. Example:

11111111 11111111 11111111 00000000 (or 255.255.255.0 in decimal notation)

Computers use Network mask, along with the IP address, to determine whether or not a destination IP address is on the same logical network.

7

The ADDing technique Do the following three Class C IP addresses

belong to the same network? 192.168.1.1, 192.168.1.50 and 192.168.2.1

IP: 11000000 10101000 00000001 00000001 192.168.1.1

Mask: 11111111 11111111 11111111 00000000 255.255.255.0

Network: 11000000 10101000 00000001 00000000 192.168.1.0/24

IP: 11000000 10101000 00000001 00110010 192.168.1.50

Mask: 11111111 11111111 11111111 00000000 255.255.255.0

Network: 11000000 10101000 00000001 00000000 192.168.1.0/24

IP: 11000000 10101000 00000010 00000001 192.168.2.1

Mask: 11111111 11111111 11111111 00000000 255.255.255.0

Network: 11000000 10101000 00000010 00000000 192.168.2.0/24

1286432168421

Network 1: 192.168.1.0/24, i.e network starting at 192.168.1.0 with network mask 255.255.255.0.Network 2: 192.168.2.0/24, i.e network starting at 192.168.2.0 with network mask 255.255.255.0.

8

Two Virtual LANs

192.168.1.1255.255.255.0

192.168.1.2255.255.255.0

192.168.1.3255.255.255.0

192.168.2.1255.255.255.0

192.168.2.2255.255.255.0

192.168.2.3255.255.255.0

Switch

9

Two interconnected LANs

10

Subnetting a class C network Suppose the 192.168.1.0/24 network You want to divide that network into two segments You can decide to use the first bit of the fourth octet as dividing point

between your network segments. So, your network mask would be:

11111111 11111111 11111111 10000000

And you will have about 27 = 128 hosts in each segment.

1286432168421

Segment 1: 192.168.1.0 to 192.168.1.127 Segment 2: 192.168.1.128 to 192.168.1.255

How to create the two segments using the ADDing technique?

11

Subnetting a class C network

IP: 11000000 10101000 00000001 00000001 192.168.1.1

Mask: 11111111 11111111 11111111 10000000 255.255.255.128

Network: 11000000 10101000 00000001 00000000 192.168.1.0/25

. . . . . .

. . . . . .

. . . . . .

. . . . . .

IP: 11000000 10101000 00000001 01111111 192.168.1.127

Mask: 11111111 11111111 11111111 10000000 255.255.255.128

Network: 11000000 10101000 00000001 00000000 192.168.1.0/25

1286432168421

Segment 1: 192.168.1.0 to 192.168.1.127

12

Subnetting a class C network

IP: 11000000 10101000 00000001 10000000 192.168.1.128

Mask: 11111111 11111111 11111111 10000000 255.255.255.128

Network: 11000000 10101000 00000001 10000000 192.168.1.128/25

. . . . . .

. . . . . .

. . . . . .

. . . . . .

IP: 11000000 10101000 00000001 11111110 192.168.1.254

Mask: 11111111 11111111 11111111 10000000 255.255.255.128

Network: 11000000 10101000 00000001 10000000 192.168.1.128/25

1286432168421

Segment 2: 192.168.1.128 to 192.168.1.255

13

Question 1 Network A is IP network 192.168.2.0/24 (i.e a

Class C network with a default 24-bit mask). Using the IP Subnet Calculator, determine the maximum number of hosts (computers) in each of the Network A’s subnets assuming that there are two subnets. You answer: ________.

Using the IP Subnet Calculator, determine the maximum number of subnets for a Class B network assuming that the four first bits of the third octet in each IP address are used as subnet bits. Your answer: _____. What is the maximum number of computers for each subnet? Your answer: ______.

14

Question 2 Consider the 192.168.2.0/24 network.

What is the maximum number of hosts in that network?

Suppose that the 192.168.2.0/24 network is segmented, and became 192.168.2.0/25

What is the maximum number of hosts in in each subnet? Would IP address 192.168.2.1 be in the same subnet as

IP address 192.168.2.126?

Consider the 192.168.2.0/24 network. You want to segment that network in order to create 4 subnets.

What would be the four (4) address ranges? What would your subnet mask be?

15

Disk Management

16

Basic disk A physical disk that can be accessed by MS-DOS and all Windows-based operating

systems. Basic disks can contain up to 4 primary partitions, or 3 primary partitions and an

extended partition with multiple logical drives.

Primary partition

1

Primary partition

2

Primary partition

3

Primary partition

4

Primary partition

1

Primary partition

2

Primary partition

3

Extended partition

• A primary partition is a portion of a physical disk that functions as though it were a physically separate disk.

• You create a primary partition, then you format it with a file system (FAT or NTFS,) and then assign a drive letter to it (e.g. C:, D:, F:, etc.)

• A primary partition can start the OS (contain the boot files)

• A special kind of partition used to create one or more logical drives

• After you create a logical drive, you format it and assign it a drive letter (e.g. G:, H:, etc.)

• An extended partition cannot start the OS.

Note: With GPT (GUID partition table) disk-partitioning scheme that is used by the Extensible Firmware Interface (EFI) in Itanium-based computers, we can create up to 128 (primary) partitions per disk

17

Dynamic disk With Win 2000, you can convert a Basic disk to a Dynamic disk With a dynamic disk, you can create an unlimited number of volumes

Volume C:

Volume D:

Volume E:

Configuration partition (1 MB)Etc….

Dynamic disks provide features that basic disks do not, such as: the ability to create volumes that span multiple disks (spanned and striped

volumes), and the ability to create fault tolerant volumes (mirrored and RAID-5 volumes).

A spanned volume is a dynamic volume consisting of disk space on more than one physical disk. Spanned volumes are not fault tolerant and cannot be mirrored.

A striped volume is a dynamic volume that stores data in stripes on two or more physical disks. Striped volumes do not provide fault tolerance. If a disk in a striped volume fails, the data in the entire volume is lost.

Special partition automatically created to store the configuration of the disk

18

Mirrored volume A fault-tolerant volume that duplicates data on two physical disks If one of the physical disks fails, the data on the failed disk becomes unavailable, but the

system continues to operate. You can create mirrored volumes only on dynamic disks.

file1 file3file2 file4

file1 file3file2 file4

19

RAID-5 volume A fault-tolerant volume with data and parity striped intermittently across three or more physical disks. Parity is a calculated value that is used to reconstruct data after a failure If a portion of a physical disk fails, Windows recreates the data that was on the failed portion from

the remaining data and parity. You can create RAID-5 volumes only on dynamic disks,

Disk 1

Disk 2

Disk 3

Disk 4

Disk 5

Parity Data Data Data Data

Data Parity Data Data Data

Data Data Parity Data Data

Data Data Data Parity Data

Data Data Data Data Parity

20

Converting Basic diskto Dynamic disk

For the conversion to succeed: any disks to be converted must contain at least 1 MB of space for

the dynamic disk database. Note: Windows 2000 automatically reserve this space when

creating partitions or volumes on a disk (This space may exist even if it is not visible in Disk Management.)

Once converted: a dynamic disk will not contain primary partitions or logical drives a dynamic disk cannot be accessed by MS-DOS, Windows 95,

Windows 98, Windows Millennium Edition, Windows NT, or Windows XP Home Edition

When you convert a basic disk to a dynamic disk: any existing partitions or logical drives on the basic disk become

simple volumes on the dynamic disk.

21

Converting Dynamic disk to Basic disk

The disk must be empty before you can change it back to a basic disk

Converting a Dynamic disk to Basic disk causes all data to be lost

If you want to keep your data, back it up or move it to another storage device

You must remove all volumes from the dynamic disk

22

Limitations of Dynamic disk

Dynamic disks are not supported on: Portable computers Removable disks Detachable disks that use Universal Serial Bus (USB)

or IEEE 1394 (also called FireWire) interfaces, Disks connected to shared SCSI buses

Dynamic volumes (and the data they contain) cannot be accessed by, or created on: Computers running MS-DOS, Windows 95,

Windows 98, Windows Millennium Edition, Windows NT 4.0, or Windows XP Home Edition

23

File system security

24

Shared Folders

To see all shared folders on a computer:1) Click Start. Then click Run2) Type \\ComputerName (where

ComputerName is a valid network computer name like SRVDC18)

3) Click OK.

To share a folder on a computer:1) Open My Computer (Right-click/Open)2) Select a disk, then the folder to share3) Right-click the selected folder4) Click Properties5) Click the Sharing tab6) Check Share this folder7) Click Apply, and then OK.

Requirements for creating a shared folder: Any supported File system (FAT, NTFS) If server in a domain, you must be Administrator or Server Operator If server in a workgroup, you must be Administrator or Power user If Client computer running a Workstation OS, you must be Administrator or

Power userNote: Users that are granted the Create Permanent Shared Objects right can

also create shared folders on the computer where the right is assigned

OR1) Open Computer Management2) In the console tree, double-click Shared

Folders3) Click Shares

25

Shared Folder Permissions Multiple Permissions (The Combination Rule)

If a user is assigned a permission for a Shared folder and

If the use user belongs to a group to which a different permission is assigned,

Then the user’s effective permissions are the combination of the user and group permissions

Deny overrides Allow

If you deny a shared folder permission to a user and

If you allow the same permission to a group the user belongs to

Then the user will not have that permission.

Copying or Moving Shared folders

If you copy a Shared folder, the original folder is shared but not the copy

If you move a Shared folder, it is no longer shared.

26

NTFS Permissions Multiple Permissions

NTFS file permissions take priority over NTFS folder permissions A user can always access files for which he/she has permissions using UNC.

E.g. \\SRVDC16\Data\file1.txt

Denying a permission for a user blocks that permission, even if the permission is granted to a group the user belongs to.

Permission Inheritance

By default, permissions assigned for the parent folder are inherited at subfolder and file level

To prevent automatic inheritance, explicit permissions assignments must be done at subfolder and/or file levels.

Copying or Moving Files and Folders

When a file/folder is moved within an NTFS partition, it retains its permissions

When a file/folder is copied to another NTFS partition, it inherits the permissions of the destination folder (Golden rule)

When a file/folder is copied to a FAT partition, it loses its NTFS permissions

27

Shares & permissions

Sharing folders/files

Setting permissions

FAT NTFS FAT NTFS

Folders/Subfolders YES YES YES (but limited)

YES

Files NO NO NO YES

28

Exercise 1 You shared a folder on a Windows 2000 Server

computer for users in your company’s London office. You place several subfolders in the London Folder as shown in the exhibit.

29

Exercise 1 (Cont.)

The Marketing-2 folder is compressed. You want to delete Marketing-2, but you want to keep all the files that are currently in the folder. You plan to copy all the files in Marketting-2 into the Marketing folder before deleting Marketing-2. You want these files to remain compressed. However, you do not want to compress any existing files in Marketing or compress any other new files added to the Marketing.

What should you do before you delete Marketing-2?

A. Copy all the files from Marketing-2 to Marketing.B. Move all the files from Marketing-2 to Marketing.C. Compress Marketing and then copy all the files from Marketing-2 to Marketing.D. Compress Marketing and then move all the files from Marketing-2 to Marketing.

30

Distributed File System, Disk Quotas

31

Dfs: Scenario 1

Problems if there are dozens of servers

Server 2

\Data

Server 3

\Sales

Server 1

\Install

Server 4

\Policy

Dfs not used Four shared folders on 4 different servers

User need to know servers and folders names to access resources

User need to connect to each server

32

Dfs: Scenario 2Server4

\Policy

Server 2

\Data

Server 1

\Install

Server 3

\Sales

Using Dfs Have a server with Dfs and Dfs links created

User need to connect to a single server

User doesn’t need to know servers and folders names

Dfs server

Link to InstallLink to PolicyLink to Data Link to Sales

33

Dfs implementation in Win 2000

Standalone DfsCreated on standalone servers (Workgroup)Doesn’t take advantage of the Active DirectoryOffer a single level of Dfs links

There are two Dfs models:

Domain-Based DfsCreated on a Domain controller or Member

server (in a Domain)Uses Active DirectoryOffer a deep hierarchy Dfs links

34

Dfs implementation in Win 2000

Only 1 Dfs root per server is allowed Dfs can be created on FAT or NTFS

partitions To create a standalone Dfs root, use the

Distributed File System snap-in

35

Disk Quotas Disk Quotas needed because

Many users save data on shared foldersUsers must be prevented from filling disk

capacity

Disk Quotas optionsEnable Disk quotas w/o limiting disk usageSet a default quota for all usersDetermine quotas on per-user basis

Disk quotas are determined based on the uncompressed files/folders sizes

36

Taking ownership1) Disk quotas are based on files/folders ownership

2) If you have the Take ownership permission on a file/folder, you can take its ownership.