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

• 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. 199.72.101.0-31

2. .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?

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