Download Discovery 2 Chapter 4 2008

4: Addressing
Working At A Small-to-Medium Business or ISP
Objectives
• Plan an IP addressing scheme
– Subnetting
– Classful
• IPv6 classless routing
• NAT & PAT
Addressing
• Every device on a network MUST have an
IP address!
– IPv4
• How many bits in an IP address?
– 32
• What’s the maximum amount of bits in an
octet?
– 256
• 192.168.1.106
– 11000000.10101000.00000001.01101010
Conversion Practice 1
• 11100101 to decimal
• 10001110 to decimal
• 11111000 to decimal
• 11111111 to decimal
Conversion Practice 2
• 192 to binary
• 224 to binary
• 47 to binary
• 115 to binary
IP Address Review- Class A
• Range:
• Default Subnet Mask:
• Which octets are Network & Host?
• How many hosts available?
Convert A
• 5 to binary
• 77 to binary
• 100 to binary
• 127 to binary
• What’s in common with all of them?
IP Address Review- Class B
• Range:
• Default Subnet Mask:
• Which octets are Network & Host?
• How many hosts available?
Convert B
• 128 to binary
• 142 to binary
• 191 to binary
• What’s in common here?
IP Address Review- Class C
• Range:
• Default Subnet Mask:
• Which octets are Network & Host?
• How many hosts available?
Convert C
• 192 to binary
• 200 to binary
• 223 to binary
• What’s common here?
Subnet Masks
• 255.255.255.0
– How many total bits are on? (1’s)
• 11111111.11111111.11111111.00000000
• /24 notation
• 255.255.0.0
– How many total bits are on? (1’s)
• 11111111.11111111.00000000.00000000
• /16 notation
• 255.255.255.248
– How many total bits are on? (1’s)
• 11111111.11111111.11111111.11111000
• /29 notation
Routers, IP’s & Subnet Masks
• Router ONLY knows which NETWORKS it
is connected to!!!
• Doesn’t care about individual hosts
• It ANDs the IP & Subnet Mask
• Result= DESTINATION NETWORK
ANDing
Subnet- Split Up the IP
• Borrow bits to make new networks
• Plan your network
– How many networks?
– How many hosts per network?
Before we do this…
• When we borrow, MUST borrow at least 2 bits or
leave at least 2 bits
– Class C has 1 octet to borrow from
– Class B has 2 octets
– Class A has 3 octets
–
–
–
–
–
22= 4
23= 8
24= 16
25= 32
26= 64
199.72.101.0
199.72.101.0
1.
2.
3.
4.
5.
6.
7.
8.
199.72.101.0-31
.32-.63 (.33-.62)
.64-.95 (.65-.94)
.96-.127 (.97-.126)
.128-.159 (.129-.158)
.160-.191 (.161- .190)
.192-.223 (.191-.222)
.224-.255
• Total Range #3
– Useable Range #2
• Network ID
– 199.72.101.64 /27
• Broadcast Address
– 199.72.101.95 /27
Assign Addresses
Router…Action!
• A packet with a destination IP of
199.72.101.85 255.255.255.224 goes to a
router
– It ANDs to come up with the NETWORK #
Keep It Private
• Inside hosts have private IP
– Only devices that connect directly to Internet
have a public IP
– Consumer ISR/Routers give out private
addresses
• What’s the Class A private?
• B?
• C?
Parts of the Network
Network
Hosts
Subnetwork
How to Work Backwards
• 221.17.125.46 /28
– What class address?
• C: Only deal with the last octet!
– 255.255.255.240
– 11111111.11111111.11111111.11110000
– How many bits borrowed?
•4
• 24= 16 networks
– How many bits left over?
•4
• 24= 16 hosts per sub-network
Work Backwards
• Based on the IP address & SM, identify…
– The network address
– The broadcast address
– How many bits were borrowed
– How many bits were left over
– Is the address valid
What’s Wrong?
• Are the hosts on the same network or
separate?
Lab
• 4.1.5
Classless Subnetting
• CIDR
• VLSM
• You can subnet, for each unequal network
– Your address is 210.1.17.64 /26
• Net A needs 37 hosts
• Net B needs 15 hosts
• Net C needs 100 hosts
CIDR Block for Router
• Instead of having multiple subnet entries for
each router port, CIDR uses the common
bits to make ONE routing table address per
port.
Running Out of Addresses
• Private Addresses
• IPv6
– 32 bits NOW 128 bits long!
– 2128 which is 3 PLUS 38 ZEROs!
NAT
• Network Address Translation
• Allows many users to use private IP
addresses inside & translates to a pool of
public IP’s for travel outside
• Purpose:
– Save public IP addresses
– So private IP computers could communicate
on the Internet
NAT in Action!
What’s the Order of NAT?
• Inside Local IP (Private) goes into your
router
• Translated to an Inside Global IP before
exiting
• Sent across Internet to Outside Local
• Outside Global sends it back to the Inside
Global
• Your router translates the Inside Global
back to the Inside Local (Private) IP
Activity
Static NAT
• Static= stays the same
• Same public IP address maps to a private
internal one
Static NAT 2
Dynamic NAT
• Has a pool of addresses
• Translates the private IP to a public &
awaits a response
– After session is closed, the public IP is
returned to the pool of addresses
Summary of NAT
• Static NAT
– Outside users need to access inside private
network
• At home, you need to access the mail server
– Static private IP is given a static public address
• Dynamic NAT
– Inside private IP host needs to access the
public Internet
– Selects from a pool of addresses
• Both can be configured at the same time
NAT Review
• Static NAT works by mapping a specific
inside local private IP address to what other
specific address type?
– Inside global
– Outside local
– Outside global
– Private IP address
PAT (or NAT Overload)
• Port Address Translation
• Used when you have very few public IP
addresses
• Translates multiple IP’s into a single public
– Uses port #’s to keep track of conversations
– Uses random source port # above 1024
PAT Review
• Which statement describes NAT overload
or PAT?
– Each internal address is dynamically translated
to an individual external IP address.
– A single internal address is always translated
to the same external IP address.
– Many internal addresses are translated to a
single IP address using different port numbers.
– Many internal addresses are statically
assigned a single IP address and port.
PAT Review
• Which port numbers are used by PAT to
create unique global addresses?
– 255 and below
– 1024 and below
– 1025 and above
– 64,000 and above
Lab
• 4.2.4
Review
4: Addressing
Working At A Small-to-Medium Business or ISP