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shaqi112
chapter_12b.pptxChapter 12b
Using TCP/IP on the Network
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Objectives
CIDR
Configuration of IP
IP utilities
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Problems with IPv4 Addresses
Problem:
Potential exhaustion of IPv4 address space (due to inefficiency)
Class B network numbers are highly prized
Not everyone needs one
Lots of class C addresses but no one wants them
Growth of back bone routing tables
We don’t want lots of small networks since this causes large routing tables
Route calculation and management requires high computational overhead
Solution:
Allow addresses assigned to a single entity to span multiple classed prefixes
Enhance route aggregation
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Classless Interdomain Routing （CIDR）
Also known as supernetting
Takes several contiguous ranges of network addresses and combines them into a larger network
Borrows bits from the network portion of the address to give to the host portion
All combined networks require only a single entry in the router tables.
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Example
The address starts at 194.24.0.0.
Suppose that Cambridge university needs 2046 addresses and is assigned 194.24.0.0 to 194.24.7.255
Oxford university asks for 4094 addresses must lie on a 4096-byte boundary.
University of Edinburgh needs 1022 ip address, assigned 194.24.8.0 to 194.24.11.255
A set of IP address assignments.
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Example
The routing tables all over the world are now updated with the three assigned entries.
Each entry contains a base address and a subnet mask.
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Example
Now consider what happens when a packet comes in addressed to 194.24.17.4 which in binary is represented as:
This value does not match the Cambridge base address.
So this address is ANDed with Edinburgh to get:
This value does not match the Cambridge base address.
So this address is ANDed with Oxford to get:
This matches the Oxford base address.
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Configuring TCP/IP
The minimum configuration
The IP address
A subnet mask
Optional configuration parameters
A gateway address
A DNS server
WINS
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Windows IP Configuration
WIN XP
Right-click on My Network Places
Click Properties
Or double-click on Network in Control Panel
Right-click on Local Area Connection
Highlight TCP/IP and click Properties
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Windows IP Configuration
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Windows IP Configuration
The gateway is the address of the device that acts as your doorway to the world outside your own network. Usually it represents the internal port of a router
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Windows IP Configuration
DNS is used to resolve domain names to IP address
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Windows IP Configuration
WINS is the Windows Internet Name Service, a protocol developed by Microsoft that resolves NetBIOS names to IP addresses.
For WINS to function, there must be a WINS server on the network.
Usually DHCP can perform
the same functions
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Windows IP Configuration
The HOSTS and LMHOSTS files are files that exist on Windows-based computers that provide mappings of IP address to host name
In the event that there are devices on the network that cannot respond to NetBIOS name query broadcasts, these files can be used to provide address resolution.
HOSTS is used to map DNS to IP address
LMHOST is used to find the NetBIOS computer names. It is used to list known IP addresses mapped with corresponding computer names
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The TCP/IP Utilities
One of the beauties of using TCP/IP as your default protocol is that it has lots of little utilities. These utilities can help the troubleshooting
Ping
Tracert
Netstat
Route
Nbtstat
IPCONFIG/IFCONFIG
Nslookup
DIG
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PING
Packet Internet Groper
Uses ICMP protocol to tell whether or not a particular host on the network is reachable.
PING works by sending out a series of ECHO packets.
The intended host, upon receiving the packets, will return an ECHO REPLY.
If the REPLY successfully, Ping will calculate the total round trip time.
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PING
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Some PING Triggers
The syntax for a ping command is:
Ping trigger host
Some of useful triggers are:
-t
A continuous PING
-a
Resolves host name to IP address
-n {count}
Sends the number of request packets defined in {count}
-i {TTL}
Sets a specific time to live for the packets as defined in {ttl}
-r {count}
Records the number of hops between target and source
-s {count}
Adds a timestamp on the number of hops specified in {count}
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Tracert
The traceroute command traces the network path of Internet routers that packets take as they are forwarded from your computer to a destination address. The "length" of the network connection is indicated by the number of Internet routers in the traceroute path.
Traceroutes can be useful to diagnose slow network connections.
For example, if you can usually reach an Internet site but it is slow today, then a traceroute to that site should show you one or more hops with either long times or marked with "*" indicating the time was really long. If so, the blockage could be anywhere from your Internet service provider to a backbone provider, and there is likely little you can do except wait with the infinite patience of the mighty oak.
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Example
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Netstat
Retrieves network statistics for any given interface on the network
netstat trigger
-a display information for all connection and active ports
-e displays all Ethernet statistics
-n display addresses and ports in numeric format
-p {protocol} display information specific to the protocol specified
-r display routing table
-s displays per-protocol statistic
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Example
Display Ethernet statistics
Display the protocol
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Route
Allows the user to create or edit local routing tables
Can retrieve and report existing routing tables on a local machine
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Route
Route print –display current local routing table
Route add –adds a static entry to local routing tables
Route delete – deletes an entry from the local routing table
Route change –modifies an existing route
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IPCONFIG / IFCONFIG
Ipconfig is the most widely used TCP/IP utility
Reports the IP configuration for all interfaces on the local machine
Can be used in conjunction with DHCP to clear and refresh IP configurations
IFCONFIG is the Linux version of IPCONFIG
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IPCONFIG / IFCONFIG
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IPCONFIG / IFCONFIG
Example
/all – shows complete configuration for all interface
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IPCONFIG / IFCONFIG
Example:
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NsLookup
Nslookup returns the domain name and ip address of any DNS server on the network
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