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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