IP Addressing (Subnetting, VLSM, Supernetting)
- 2. IP Address • IP address is a logical address given to each and every device in a network. • It is used to identify specific device in the network. • However, an IP address can represent a complete network, a specific host, or the broadcast address of the network. • It is divided into Network portion/Prefix and Host portion. • There are two versions of IP address: IPv4 and IPv6 Network Set of devices Host A specific device on the network
- 3. IP Version 4 • An IPv4 address is 32 bits long — 4 separate bytes. • It is represented in dotted-decimal notation — each byte represents a decimal number separated by a period. • Network ID: First IP of a range. All 0’s in the host portion. Reserved for identifying the complete network. • Broadcast Address: Last IP of a range. All 1’s in the host portion. Used to send broadcast to all within the same network. • Valid IP: Lies between the Network and Broadcast addresses. Only these can be assigned to the hosts. IPv4 Address Range 0.0.0.0 to 255.255.255.255
- 4. Subnet Mask • A separate 32-bit pattern to Identify the division of the network and the host portion of an address. • It says where to look for these portions in a given address. Valid Subnet Masks
- 5. Subnet Mask (contd.) • In CIDR notation, the number of 1’s in the mask’s binary version is counted from the left and that number is appended to the end of the base address following a slash (/). • Subnet masks are used to make routing decisions. • The Default Subnet Mask is the number of bits that are reserved by the address class. Using the default mask will accommodate only one network subnet in the relative class. • A Custom Subnet Mask can be defined by an administrator to accommodate many network subnets.
- 6. Subnet Mask (contd.) Using the default class mask:
- 7. Subnet Mask (contd.) Using a custom subnet mask:
- 8. Types of IPv4 Address Private IP Address • Hosts that do not require access to the Internet can use private addresses. • These are not routed by Internet routers. Class Range CIDR Block # of Hosts Class A 10.0.0.0 to 10.255.255.255 10.0.0.0/8 16777216 Class B 172.16.0.0 to 172.31.255.255 172.16.0.0/16 1048576 Class C 192.168.0.0 to 192.168.255.255 192.168.0.0/24 65536
- 9. Types of IPv4 Address (contd.) Public IP Address • Globally unique addresses that are recognized on the Internet. Real IP Address • Public addresses which are registered through the IANA.
- 10. Types of IPv4 Address (contd.) Special IP Addresses • 127.X.X.X — “loopback” Used by hosts to direct traffic to themselves and for testing purpose. • 0.0.0.0 — “this host on this network” Used during DHCP initialization phase. Host uses IP for communication with DHCP server but has no address assigned so far. • 0.X.X.X — “invalid/unspecified”
- 11. Classfull Addressing • The ‘Class’ identifies the default point of separation. • IP addresses, left in their classful state, yield exactly one subnet. # of networks and hosts in the classfull scheme
- 12. Classless Addressing • Formal name is Classless Inter-Domain Routing (CIDR). • The class privilege was removed from the distribution to compensate for the address depletion. • Instead of having three distinct address classes, this mechanism allows the division between prefix and suffix to occur on an arbitrary bit boundary. • To do so, the addressing scheme stores a 32-bit subnet mask along with each address.
- 13. Subnetting • Subnetting is the process of dividing a single network into multiple smaller networks. • It helps in minimizing the wastage of IP address. • It offers containment of broadcast traffic within subnetwork which improves network performance. • In many cases, subnets are created to serve as physical or geographical separations.
- 14. Subnetting (contd.) • Each subnet is a non-physical description/ID for a physical subnetwork – usually a switched network of host containing a single router in a multi-router network. • A router is necessary for devices on different networks and subnets to communicate. • Each router interface must have an IPv4 host address that belongs to the network or subnet that the router interface is connected to. • Devices on a network and subnet use the router interface attached to their LAN as their default gateway.
- 15. Subnetting (contd.) • Creating sub-networks is the act of taking bits from the host portion of the address and reserving them to define the subnet address instead. • Clearly this will result in fewer bits being available for defining hosts. • Subnetting can be performed in two ways: FLSM (Fixed Length Subnet Masking) VLSM (Variable Length Subnet Masking) • Subnetting is done based on requirement. Requirement of Hosts 2 𝐻 − 2 ≥ 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡 Requirement of Networks 2 𝑁 ≥ 𝑅𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡
- 16. FLSM – Example 1
- 17. FLSM – Example 2
- 18. FLSM – Example 3 • A service provider has given you the Class C network range 209.50.1.0 Your company must break the network into 20 separate subnets.
- 19. FLSM – Example 4 • Your company would like to break the Class B private IP address range 172.16.0.0 into as many subnets as possible, provided that they can get at least 300 clients per subnet.
- 20. FLSM – Example 5 • You are given the IP address 192.168.1.58/28 Identify the original range of addresses (the subnet) that this IP address belongs to.
- 21. FLSM – Example 6
- 22. FLSM – Example 7
- 23. FLSM – Example 8
- 24. FLSM – Example 8 (contd.)
- 25. FLSM – Example 9
- 26. FLSM – Example 9 (contd.)
- 27. FLSM – Example 10 An ISP is granted a block of addresses starting with 190.100.0.0/16. The ISP needs to distribute these addresses to three groups of customers as follows: • The first group has 64 customers; each needs 256 addresses. • The second group has 128 customers; each needs 128 addresses. • The third group has 128 customers; each needs 64 addresses. Design the subblocks and find out how many addresses are still available after these allocations.
- 28. FLSM – Example 10 (contd.) For Group-1, each customer needs 256 addresses. This means 8 bits are needed to define each host. The prefix length is 32 - 8 = 24. The addresses are: 1st Customer: 190.100,0.0/24 ---------- 190.100.0.255/24 2nd Customer: 190.100.1.0/24 ---------- 190.100.1.255/24 .......... 64th Customer: 190.100.63.0/24 -------190.100.63.255/24 Total = 64 x 256 = 16,384 For Group-2, each customer needs 128 addresses. This means 7 bits are needed to define each host. The prefix length is 32 - 7 = 25. The addresses are: 1st Customer: 190.100.64.0/25 -------- 190.100.64.127/25 2nd Customer: 190.100.64.128/25 -------- 190.100.64.255/25 ........ 128th Customer: 190.100.127.128/25 -------- 190.100.127.255/25 3. Total = 128 x 128 = 16,384
- 29. FLSM – Example 10 (contd.) For Group-3, each customer needs 64 addresses. This means 6 bits are needed to each host. The prefix length is 32 - 6 = 26. The addresses are: 1st Customer: 190.100.128.0/26 ---- 190.100.128.63/26 2nd Customer: 190.100.128.64/26 ---190.100.128.127/26 ........ 128th Customer: 190.100.159.192/26 ---- 190.100.159.255/26 Total = 128 x 64 = 8192 # of granted addresses to the ISP: 65536 # of allocated addresses by the ISP: 40960 # of available addresses: 24576
- 30. VLSM • VLSMs can use subnet masks with different lengths for different router interfaces. • Allows a network space to be divided in unequal parts. • Subnet mask will vary depending on how many bits have been borrowed for a particular subnet. • Used frequently if public address are used internally or unplanned growth needs to be accommodated inside of a site. • Results in less waste on smaller subnets where fewer addresses are necessary. Subnetting a subnet
- 31. VLSM (contd.)
- 32. VLSM (contd.) Applying VLSM to a Network Design
- 33. VLSM (contd.)
- 34. VLSM – Example 1
- 35. VLSM – Example 1 (contd.)
- 36. VLSM – Example 1 (contd.)
- 37. VLSM – Example 1 (contd.)
- 38. VLSM – Example 1 (contd.)
- 39. VLSM – Example 2 • For 100 hosts: 2^h-2>=100, hence h=7 (host bits) Hence value is 8+8+8+(8-7)=25 Hence subnet mask is 11111111.11111111.11111111.10000000 i.e.255.255.255.128 Block size is 2^7=128 hence the range is 192.168.1.0/25 to 192.168.1.127/25 for 100 hosts Given the no of hosts as 100, 50 20 & 6. Find IP addresses and subnet mask for 192.168.1.0
- 40. VLSM – Example 2 (contd.) • For 50 hosts: 2^h-2>=50, hence h=6 (host bits) Hence value is 8+8+8+(8-6)=26 Hence subnet mask is 11111111.11111111.11111111.11000000 i.e.255.255.255.192 Block size is 2^6=64 hence the range is 192.168.1.128/26 to 192.168.1.191/26 for 50 hosts • For 20 hosts: 2^h-2>=20, hence h=5 (host bits) Hence value is 8+8+8+(8-5)=27 Hence subnet mask is 11111111.11111111.11111111.11100000 i.e.255.255.255.224 Block size is 2^5=32 hence the range is 192.168.1.192/27 to 192.168.1.223/27 for 20 hosts
- 41. VLSM – Example 2 (contd.) • For 6 hosts: 2^h-2>=6, hence h=3 (host bits) Hence value is 8+8+8+(8-3)=29 Hence subnet mask is 11111111.11111111.11111111.11111000 i.e.255.255.255.248 Block size is 2^3=8 hence the range is 192.168.1.224/29 to 192.168.1.231/29 for 6 hosts • Complete range: 192.168.1.0/25 to 192.168.1.127/25 for 100 hosts 192.168.1.128/26 to 192.168.1.191/26 for 50 hosts 192.168.1.192/27 to 192.168.1.223/27 for 20 hosts 192.168.1.224/29 to 192.168.1.231/29 for 6 hosts
- 42. Supernetting • It provides route updates in the most efficient way possible by advertising many routes in one advertisement instead of individually. • Its purpose is to reduce the size of routing tables on routers to save memory, which also shortens the amount of time IP requires to parse the routing table when determining the best path to a remote network. • It works only if the network is designed properly. • By creating contiguous blocks of addresses to specific areas of a network, one can then easily summarize the network and keep route updates with a routing protocol to a minimum. • If IP subnets are carelessly handed out to any location on the network, there will no longer be any summary boundaries.
- 45. Supernetting – Example 1
- 46. Supernetting – Example 2
- 47. Supernetting – Example 2 (contd.)
- 48. Supernetting – Example 2 (contd.)