Network IP Address Planning for IPv6 & IPv4

Network IP Address Planning

The Network IP Address Planning is required for the allocation of the address space to design a computer network. Network subnet planning requires an analysis of both the organization's network usage needs and how the subnets will be structured. The starting point is to carry out a study of the network requirements.

IP Address Planning

The IP Address Planning includes to determining the following:

• The needs of each subnet in terms of size
• Number of hosts per subnet
• The way host addresses will be assigned
• Which are the hosts that will require static IPv4 addresses and which ones can use DHCP

The network administrator decides the range of private IPv4 addresses used in a LAN, and should carefully consider it to ensure that there are enough host addresses available for known hosts so far and for future expansions. Remember that the ranges of private IPv4 addresses are as follows:

• 10.0.0.0 to 10.255.255.255, with subnet mask 255.0.0.0 or / 8
• 172.16.0.0 to 172.31.255.255, with subnet mask 255.240.0.0 o / 12
• 192.168.0.0 to 192.168.255.255, with subnet mask 255.255.0.0 or / 16

Learn about IP subnetting

Main Consideration while IP Address Planning

The assignment of network addresses should be planned and recorded for the following purposes:

• Avoid duplication of addresses : Without proper planning and registration, one address could be assigned to more than one host, which would cause access problems for both hosts.
• Provide and control access : The Layer 3 address assigned to a server can be used to control access to that server.
• Control security and performance : To easily find problematic network devices.

 ASSIGNING ADDRESSES TO DEVICES

Within a network, there are different types of devices that require addresses, some common devices are:

• End user customers : Most networks assign addresses dynamically with the Dynamic Host Configuration Protocol (DHCP).
• Servers and peripherals (eg printers): they must have a predictable static IP address.
• Servers that can be accessed via the Internet : In most cases, these servers are assigned private addresses internally, and the router or firewall on the perimeter of the network must be configured to translate the internal address to a public address .
• Intermediary devices : Because it is necessary to know how to communicate with intermediary devices, these must have assigned predictable and static addresses.
• Gateway : Normally, the router interface uses the lowest or highest address in the network.

Example network addressing plan: 192.168.1.0/24

USE	FIRST	LAST
Host devices	.one	.229
Servers	.230	.239
Printers	.240	.249
Intermediary Devices	.250	.253
Gateway	.254

DESIGN CONSIDERATIONS FOR IPV6

IPv6 subnetting requires a different approach than IPv4 subnetting. The same reasons for subnetting the IPv4 address allocation space to manage network traffic also apply to IPv6. However, due to the large number of IPv6 addresses, it is no longer necessary to worry about conserving addresses. In IPv6 subnetting, address space conservation is not a problem to consider. The subnet ID includes more subnets than enough. IPv6 subnetting has to do with creating an addressing hierarchy based on the number of subnets needed.

Remember that there are two types of assignable IPv6 addresses: a link-local IPv6 address is never subdivided, since it only exists on the local link; however, a global unicast IPv6 address can be divided.

GLOBAL UNICAST IPV6 ADDRESS

The global unicast IPv6 address usually consists of a global routing prefix / 48, a 16-bit subnet ID and a 64-bit interface ID.

 SUBNETTING BY SUBNET ID

The 16-bit subnet ID section of the global unicast IPv6 address can be used to create internal subnets. The subnet ID provides more subnets than necessary and supports more hosts than may be needed for a subnet. For example, the 16-bit section allows you to do the following:

• Create up to 65,536 subnets / 64. This does not include the ability to borrow bits from the address interface ID.
• Support up to 18 trillion host IPv6 addresses per subnet (e.g., 18,000,000,000,000,000,000).

 IPV6 SUBNET ASSIGNMENT

With the ability to choose from more than 65,000 subnets, the task of the network administrator becomes the task of designing a logical scheme to address the network. As shown in image 1, the topology used as an example will require subnets for each LAN, as well as for the WAN link between R1 and R2. With IPv6 the subnet of the WAN link is not further divided into subnets. Although this may cause the "waste" of addresses, that is not a cause for concern when using IPv6.

As shown in image 2, for this example the assignment of five IPv6 subnets is used, with the subnet ID field from 0001 to 0005. Each subnet / 64 will provide more addresses than will ever be needed.

Finally, the configuration for Router 1 (R1) would be as follows:

R1 (config) # interface gigabitethemet 0/0 

R1 (config-if) # ipv6 address 2001: db8: acad: 1 :: 1/64 

R1 (config-íf) # exit 

R1 (config) # interface gigabitethernet 0/1 

R1 (config-if) # ipv6 address 2001: db8: acad: 2 :: 1/64 

R1 (config-if) # exit 

R1 (config) # interface serial 0/0/0 

R1 (config-if) # ipv6 address 2001 : db8: acad: 3 :: 1/64 

R1 (config-íf) # end 

R1 #