Classful IP Address (IP Address Picture Book-4 from VisualLand Animations)

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Classful IP AddressIP Address picture book
4www.visualland.net

• Watch animation to learn networking.
• Present IP addresses in A, B, C, D classes by
  byte boundary with a.4-digit form (a.b.c.d) and
  show how routing table does lookup.
• This pictured tutorial takes screenshots from
  Classful IP Address Animation.
• OK to republish this slide. Please use hyperlink
  to point to its source.

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IP Address animations

• 1. Why IP address? Shows how IP addresses are
  being used when computers are transmitting
  messages. Each packet is tagged by a sender and a
  receiver's IP address.
• 2. How Internet Forwards Packets? Computers
  are connected to Internet via gateway routers.
  Routers use routing table to make packet
  forwarding decisions.
• 3. Network Address. A 32-bit IP address is
  divided into network ID (left bits) and host ID
  (right bits). Router uses network addresses to
  forwad packets.
• 4. Classful IP Address. Present IP addresses
  in A, B, C, D classes by byte boundary with
  a.4-digit form (a.b.c.d) and show how routing
  table does lookup.
• 5. Subnettiing - Classless IP address It uses
  a class B address and its 5 subnets as an
  examples to show how routing table lookup works
  with different network mask.
• 6. VLSM Show a good subnetting design case
  that aggregatrd routes in a routing table. Ans
  show a bad case that cannot aggregate routes.

2019/9/23
www.visualland.net
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Overview Classful IP, routing table Animation
Link
Goal Use examples to show how classful IP
addresses are being used by routers to forward
packets. Topology 3 computerrs are assigned
class A, B, C addresses. They are connecred to a
router R1. Steps 1) Jack ping Rose. R1 lookup
network address and forwards ping to Rose
2) Rose responds by sending an Echo back to
Jack. R1 forwards it to Jack. 3) Jack
ping Tom in the same network as Mary. Tom is
offline. Mary recevies ping and drops it.
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Classful IP

• IP address contains 4 bytes. Classful IP address
  use the leftmost 1, 2, or 3 bytes for network
  addresses.
• - Class A The leftmost byte is used for network
  address. There are 256 class A networks. Each
  contains
• 16,777,214 host addresses. E.g., 100.4.5.6/8's
  network address is 100.0.0.0.0
• - Class B Two leftmost bytes are used for
  network address. e.g., 150.1.2.3/16's network
  address is 150.1.0.0.0
• - Class C The left 3 bytes are network address.
  There are 16,777,214 class A networks. Each
  contains 256
• host addresses. E.g., 222.111.44.33/24, network
  address is 222.111.44.0

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Classful IP

• IP address contains 4 bytes. Classful IP address
  use the leftmost 1, 2, or 3 bytes for network
  addresses.
• - Class A The leftmost byte is used for network
  address. There are 256 class A networks. Each
  contains
• 16,777,214 host addresses. E.g., 100.4.5.6/8's
  network address is 100.0.0.0.0
• - Class B Two leftmost bytes are used for
  network address. e.g., 150.1.2.3/16's network
  address is 150.1.0.0.0
• - Class C The left 3 bytes are network address.
  There are 16,777,214 class A networks. Each
  contains 256
• host addresses. E.g., 222.111.44.33/24, network
  address is 222.111.44.0

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Classful IP

• IP address contains 4 bytes. Classful IP address
  use the leftmost 1, 2, or 3 bytes for network
  addresses.
• - Class A The leftmost byte is used for network
  address. There are 256 class A networks. Each
  contains
• 16,777,214 host addresses. E.g., 100.4.5.6/8's
  network address is 100.0.0.0.0
• - Class B Two leftmost bytes are used for
  network address. e.g., 150.1.2.3/16's network
  address is 150.1.0.0.0
• - Class C The left 3 bytes are network address.
  There are 16,777,214 class A networks. Each
  contains 256
• host addresses. E.g., 222.111.44.33/24, network
  address is 222.111.44.0

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Classful IP

• IP address contains 4 bytes. Classful IP address
  use the leftmost 1, 2, or 3 bytes for network
  addresses.
• - Class A The leftmost byte is used for network
  address. There are 256 class A networks. Each
  contains
• 16,777,214 host addresses. E.g., 100.4.5.6/8's
  network address is 100.0.0.0.0
• - Class B Two leftmost bytes are used for
  network address. e.g., 150.1.2.3/16's network
  address is 150.1.0.0.0
• - Class C The left 3 bytes are network address.
  There are 16,777,214 class A networks. Each
  contains 256
• host addresses. E.g., 222.111.44.33/24, network
  address is 222.111.44.0

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Jack Ping Rose
Jack ping Rose. Ping's destiination IP address is
Rose's IP address 150.1.2.3/16. This is a class
B address (150 is between 128191). It's mask is
/16. It means that a 32 bit IP address is
divided into two parts, the left 16 bits is
network ID (150.1), the network ip address is
150.1.0.0 The right 16 bits is host ID
(2.3). Note See more IP address classification
details in FAQ.
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R1 forwards ping to Mary
When R1 receives ping, it reads destination IP
address (150.1.2.3/16), extracts network address
(150.1.0.0/16) and uses network address to
lookupop its routing table. A match is found
(150.1.0.0/16, Port2). R1 forwards ping to Port2
and delivers poing to next hop. Note See more
details in FAQ for the relastionships between IP
address, class, mask, network address, routing
table entry.
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Rose sends Echo to Jack
When Rose receives Ping. It responds an Echo back
to Jack. Echo's destination address is Jack's IP
addtress 100.4.5.6. It's the sender's address of
Ping. This is a class A address (100 is between
0127). Network mask is /8 The leftmost 8 bit
is used for network ID, the rightmost 24 bit is
used for host ID.
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R1 forwards Echo to Jack
When R1 receives Echo, it extracts netwrok
address (100.0.0.0/8) from Echo's destination
address (100.4.5.6/.8) and uses network address
to lookup its routing table. A mtch is found
(100.0.0.0/8, Port1). R1 forwards Echo to Port1.
Ping is delviered to next hop (Jack).
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Jack ping Tom
Jack ping Tom. Tom's IP is 222.111.44.50/24, a
class C address (222 is between 192223). When R1
receives ping, it uses Ping's destination
network address 222.111.44.0/24 to lookup its
routing table. A match is found
(222.111.44.0/24, Port3). R1 forwards Ping to
Port3 and deliviers it to network
222.111.44.0/8. Note Router's job is to forwards
packets to next hop. It does not know whether the
target host exist or not. Note Tom and Mary
(222.111.44.33/24) have the same network address
222.111.44.0/8
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Jack ping Tom
Jack ping Tom. Tom's IP is 222.111.44.50/24, a
class C address (222 is between 192223). When R1
receives ping, it uses Ping's destination
network address 222.111.44.0/24 to lookup its
routing table. A match is found
(222.111.44.0/24, Port3). R1 forwards Ping to
Port3 and deliviers it to network
222.111.44.0/8. Note Router's job is to forwards
packets to next hop. It does not know whether the
target host exist or not. Note Tom and Mary
(222.111.44.33/24) have the same network address
222.111.44.0/8
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Tom is offline
Ping is forwarded to 222.111.44.0/24 network.
This is an Ethernet Local Area network. All nodes
will receive this ping. In this network, Ping
reaches Mary and Tom. Mary receives this ping and
drops it due to mis-match. Tom is offline and
drops the ping.
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FAQ

• What is IP address classes?
• How to classify IP address?
• How many host IDs and network IDs for class A, B,
  C addresses?
• How to determine classes when IP addresses are
  presented in binary?
• How well does classful address work?
• ( answers in the Comments box )

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