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Chapter 8: Division of IP networks into subnets (Division into subnetworks…
Chapter 8: Division of IP networks into subnets
Broadcast domains
the devices use the broadcast to identify to locate the DHCP server and detect the associated MAC address.
Design
implementation
administration
IP address assignment
Problems with large broadcast domains
A large broadcast domain is a network that connects many hosts.
slow network because of the significant amount of traffic
slow devices because a device must accept and process each packet
Reasons to subnet
Location
Organization unit
Type of device
Any other division that makes sense for the network
Boundaries of the octet
Prefix length /8 /16 /24
subnet mask
Subnet mask in binary system
Host amount (16.777.214 - 65.534 - 254)
Subnetting in the octet boundary
network division 10.x.0.0 / 16 in subnets
256 possible subnets
65,534 possible hosts for subnet
diffusion
Division into subnetworks without class
prefix length /25 /26 /27 /28 /29 /3
the number of available subnets is doubled
Row / 25: Borrowing 1 bit from the fourth octet creates 2 subnets that each support 126 hosts.
Row / 26: Borrowing 2 bits creates 4 subnets that each support 62 hosts.
Row / 27: Borrowing 3 bits creates 8 subnets that each support 30 hosts.
Row / 28: Borrowing 4 bits creates 16 subnets that each support 14 hosts.
Row / 29: Borrowing 5 bits creates 32 subnets that each support 6 hosts.
Creation of two subnets
Each LAN has one of the subnets assigned.
The R1 has two LAN segments
The router interfaces must have a valid host IP address assigned to the corresponding subnet.
the configuration for the R1 interfaces with the first IPv4 address
the host of PC2 on the network 192.168.1.128/25.
Subnetting formulas
2^n n=borrowed bits
To calculate the number of hosts that can be supported
2^n-2 n=number of bits remaining in the host field
Creation of four subnets
The company uses the private network address range
By using the formula 2 ^ n for the two bits that were borrowed
All four subnets use the resulting subnet mask / 26
After borrowing 2 bits for the subnet, subtract 6 host bits.
The significant addresses of the first subnet
the specifications of the first three sub-networks that will be used to comply with the topology of Figure 1 are shown
the first valid host address of each subnet is applied to the LAN network interface
Creating subnets with a / 16 prefix
an IPv4 network with more host bits is required to borrow.
255.255.0.0 o / 16. This address has 16 bits in the network portion and 16 bits in the host portion.
Do not be intimidated by the size of the table. The reason for its large size is that it has 8 additional bits
Creation of 100 subnets with a network / 16
private address 172.16.0.0/16
start taking them from the third octet from left to right.
Borrow a single bit at a time until the amount of bits needed to create 100 subnets is reached
To comply with the requirements of the company, you would have to borrow 7 bits (eg: 2 ^ 7 = 128 subnets)
Calculation of hosts
examine the third and fourth octets.
borrow 7 bits for the subnet
subtract 1 host bit in the third octet and 8 host bits in the fourth octet
gives a total of 9 bits that were not borrowed.
There are only 510 host addresses available for each subnet / 23
the first host address for the first subnet is 172.16.0.1, and the last host address is 172.16.1.254.
Subnetting based on need for hosts
consider
The number of individual subnets needed
The number of host addresses that are required for each network
The more bits that are borrowed to create subnets, the lower the number of available host bits.
so that the usable amount of addresses can be calculated by the formula 2 ^ n - 2
Global unicast IPv6 address
48-bit global routing prefix
Subnet ID 16 bits
64 bit interface ID
IPv6 subnet assignment
more than 65,000 possible subnets
with IPv6 the subnet of the WAN link does not continue to be subnetted
Each subnet / 64 will provide more addresses
a subnet / 64 is assigned to each LAN segment and to the WAN link.