Date post: | 02-Jan-2016 |
Category: |
Documents |
Upload: | sabrina-shepherd |
View: | 214 times |
Download: | 0 times |
CS
4500
Dr. Clincy Lecture 2
Multihomed devices• As we mentioned, any device with one or more connections to the
Internet will need an IP address for EACH connection – such devices are called “multihomed” devices.
• A Router could be a multihomed device
CS
4500
Dr. Clincy Lecture 3
Example of direct broadcast address
Example of limited broadcast address
If the hostid is all 1’s, it’s called a “broadcast address” and the router use it to send a packet to all host in a specific network. In this case, hosts 20, 64, 126 and etc. will receive the packet from the router
If the hostid and netid are all 1’s, it’s called a “limited broadcast address”. If the host wants to send a packet to all host in a specific network, it would use this address. The router would block this address so that data stays contained within a specific network.
Router sending to all hosts on a network
Host sending to all other hosts on a network
CS
4500
Dr. Clincy Lecture 4
Example of this host on this address
Example of specific host on this network
An address of all 0’s is used during bootstrap time if the host doesn’t know it’s IP address. The un-named host sends an all 0 source address and limited broadcast (all 1’s) destination address to the bootstrap server.
An address with a netid of all 0’s is used by a host or router to send another host with in the same network a message.
Host sending to some other specific host on a network
IP-less Host sending message to bootstrap server
CS
4500
Dr. Clincy Lecture 5
Example of loopback address• The IP address with the 1st byte equal to 127 is used for the loop back address.
• Loopback address is used to test software on a machine – the packet never leaves the machine – it returns to the protocol software
• Example: a “ping” command can send a packet with a loopback address as the destination address to see if the IP software is capable of receiving and processing a packet.
CS
4500
Dr. Clincy Lecture 8
SUBNETTING
• When we talked about CLASSFUL addressing – we realized the problem of wasted host addresses and depleting available network addresses.
• In subnetting, a network is divided into several smaller networks called subnetworks or subnets – each subnet will have it’s own address
• Typically, there are 2 steps in reaching a destination: first we must reach the network (netid) and then we reach the destination (hostid)
CS
4500
Dr. Clincy Lecture 9
A network with two levels ofhierarchy (not subnetted)
The 2 level approach is not enough some times – you can only have 1 physical network – in example, all host are at the same level – no grouping
CS
4500
Dr. Clincy Lecture 10
A network with three levels ofhierarchy (subnetted)
With subnetting, hosts can be grouped
(0-63) (64-127)
(192-255)
(128-191)
CS
4500
Dr. Clincy Lecture 11
Addresses in a network withand without subnetting
With subnetting, there are 3 levels (versus 2 levels). Partition the hostid space into subnetid and hostid.
(1st) network, (2nd) subnetwork and (3rd) host
CS
4500
Dr. Clincy Lecture 14
Finding the Subnet Address
Given an IP address, we can find the subnet address the same way we found the network address in the previous chapter. We apply the mask to the address. We can do this in two ways: straight or short-cut.
Straight Method
In the straight method, we use binary notation for both the address and the mask and then apply the AND operation to find the subnet address.
Short-Cut Method
** If the byte in the mask is 255, copy the byte in the address.
** If the byte in the mask is 0, replace the byte in the address with 0.
** If the byte in the mask is neither 255 nor 0, we write the mask and the address in binary and apply the AND operation.
CS
4500
Dr. Clincy Lecture 15
Subnet Mask Form
• In the early days, non-contiguous 1’s masks were used (0’s and 1’s could alternate)
• Today, as a best practice, contiguous 1’s masks are used
• In either case, the black box can perform the “masking” process
CS
4500
Dr. Clincy Lecture 16
Example 1Example 1
What is the subnetwork address if the destination address is 200.45.34.56 and the subnet mask is 255.255.240.0?
Solution
11001000 00101101 00100010 00111000
11111111 11111111 11110000 00000000
11001000 00101101 001000000000 0000000000000000
The subnetwork address is 200.45.32.0.
CS
4500
Dr. Clincy Lecture 17
0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0 1 0 1 0 0 1 1 0 0 0 1 1 1 0 1 0 0 0 0 1 0 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 0 0 1 1 1 1 1 0 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 1 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 1 1 1 1 0 0 0 1 1 0 0 1 1 1 0 1 0 1 1 0 1 1 1 1 1 0 0 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1
1-bit Netid case (no subnets)
16 addresses/block
Number of blocks: 2
Address range per block: 0 to 15
Netids: 0, 1
Network Addresses : 00000, 10000
Broadcast Addresses: 01111, 11111
Recall - 5-bit Address Space Illustration
CS
4500
Dr. Clincy Lecture 18
0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0 1 0 1 0 0 1 1 0 0 0 1 1 1 0 1 0 0 0 0 1 0 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 0 0 1 1 1 1 1 0 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 1 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 1 1 1 1 0 0 0 1 1 0 0 1 1 1 0 1 0 1 1 0 1 1 1 1 1 0 0 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1
1-bit Subnet case
Number of blocks/networks: 2
Number subnets per block: 2
8 addresses/subnet
Address range per subnet: 0 to 7
Subnet ids: 0, 1
Network Addresses : 00000, 01000, 10000, 11000
Broadcast Addresses: 00111, 01111, 10111, 11111
5-bit Address Space Illustrationsubnet
CS
4500
Dr. Clincy Lecture 19
0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0 1 0 1 0 0 1 1 0 0 0 1 1 1 0 1 0 0 0 0 1 0 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 0 0 1 1 1 1 1 0 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 1 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 1 1 1 1 0 0 0 1 1 0 0 1 1 1 0 1 0 1 1 0 1 1 1 1 1 0 0 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1
2-bit Subnet case
Number of blocks/networks: 2
Number subnets per block: 4
4 addresses/subnet
Address range per subnet: 0 to 3
Subnet ids: 00, 01, 10, 11
Network Addresses : 00000, 00100, 01000, 01100 10000, 10100, 11000, 11100
Broadcast Addresses: 00011, 00111, 01011, 01111 10011, 10111, 11011, 11111
5-bit Address Space Illustrationsubnet
CS
4500
Dr. Clincy Lecture 20
0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0 1 0 1 0 0 1 1 0 0 0 1 1 1 0 1 0 0 0 0 1 0 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 0 0 1 1 1 1 1 0 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 1 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 1 1 1 1 0 0 0 1 1 0 0 1 1 1 0 1 0 1 1 0 1 1 1 1 1 0 0 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1
What is the mask ? 10000
If address 11101 is masked, what is the result ?
Illustrating the mask concept (1 of 3)netid
1 0 0 0 0
address
result
CS
4500
Dr. Clincy Lecture 21
0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0 1 0 1 0 0 1 1 0 0 0 1 1 1 0 1 0 0 0 0 1 0 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 0 0 1 1 1 1 1 0 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 1 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 1 1 1 1 0 0 0 1 1 0 0 1 1 1 0 1 0 1 1 0 1 1 1 1 1 0 0 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1
Illustrating the mask concept (2 of 3)subnet
What is the mask (subnet mask) ? 11000
If address 11101 is masked, what is the result ?
1 1 0 0 0
address
result
CS
4500
Dr. Clincy Lecture 22
0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0 1 0 1 0 0 1 1 0 0 0 1 1 1 0 1 0 0 0 0 1 0 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 0 0 0 1 1 0 1 0 1 1 1 0 0 1 1 1 1 1 0 0 0 0 1 0 0 0 1 1 0 0 1 0 1 0 0 1 1 1 0 1 0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 1 1 1 1 0 0 0 1 1 0 0 1 1 1 0 1 0 1 1 0 1 1 1 1 1 0 0 1 1 1 0 1 1 1 1 1 0 1 1 1 1 1
Illustrating the mask concept (3 of 3)subnet
What is the mask (subnet mask) ? 11100
If address 11101 is masked, what is the result ?
1 1 1 0 0
address
result
CS
4500
Dr. Clincy Lecture 23
Example 2Example 2
What is the subnetwork address if the destination address is 19.30.84.5 and the mask is 255.255.192.0?
CS
4500
Dr. Clincy Lecture 24
Comparison of a default mask and a subnet mask
A portion of the hostid space is divided between some contiguous 1’s and 0’s
CS
4500
Dr. Clincy Lecture 25
The number of subnets must be The number of subnets must be a power of 2. a power of 2.
Determine the number of subnets added by looking at the number of 1s added to Determine the number of subnets added by looking at the number of 1s added to the default mask and performing 2 raised to that numberthe default mask and performing 2 raised to that number
For example, 23 = 8 subnets
CS
4500
Dr. Clincy Lecture 26
Example 3Example 3
A company is granted the site address 201.70.64.0 (class C). The company needs six subnets. Design the subnets.
SolutionSolutionThe number of 1s in the default mask is 24 (class C).
The company needs six subnets. This number 6 is not a power of 2. The next number that is a power of 2 is 8 (23). We need 3 more 1s in the subnet mask. The total number of 1s in the subnet mask is 27 (24 3).
The total number of 0s is 5 (32 27). The mask would be
CS
4500
Dr. Clincy Lecture 27
Solution (Continued)Solution (Continued)
11111111 11111111 11111111 11100000or
255.255.255.224
The number of subnets is 8.The number of addresses in each subnet is 25 (5 is the number of 0s) or 32.
CS
4500
Dr. Clincy Lecture 29
Example 4Example 4 A company is granted the site address 181.56.0.0 (class B). The company needs 1000 subnets. Design the subnets.
SolutionSolution The number of 1s in the default mask is 16 (class B).
The company needs 1000 subnets. This number is not a power of 2. The next number that is a power of 2 is 1024 (210). We need 10 more 1s in the subnet mask.
The total number of 1s in the subnet mask is 26 (16 10).
The total number of 0s is 6 (32 26).
The mask is
11111111 11111111 11111111 11000000
or
255.255.255.192.
The number of subnets is 1024.
The number of addresses in each subnet is 26 (6 is the number of 0s) or 64.