4: AddressingWorking 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

• Convert 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, total & useable?

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

199.72.101.01. 199.72.101.0-312. .32-.63 (.33-.62)3. .64-.95 (.65-.94)4. .96-.127 (.97-.126)5. .128-.159

(.129-.158)6. .160-.191

(.161- .190)7. .192-.223

(.191-.222)8. .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 NetworkNetwork

Subnetwork

Hosts

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?

Questions• What’s the broadcast address for

201.78.90.0 /24?– 201.78.90.255– Default SM, no subnetting

• Sam’s Beef Hut uses network 215.67.106.0 & 255.255.255.240 to create subnets. How many useable hosts can be created per network?– 14

Questions• Which class gives you the most

hosts/network?– A

• Which class give you the most networks?– C

• Public IP addresses must be __________.

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: AddressingWorking At A Small-to-Medium Business or ISP