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IPv4 Addressing Plan

1. What is an IP addressing plan?

An IP addressing plan is a document usually developed by network/design engineers to show how the IP addresses will be distributed among the network devices based on the network architecture or topology in a way that support the required services. 

2. What are the benefits?

The IP addressing plan:

  • will determine the number of IP addresses required immediately and in the long term to deliver the specified services to your customers.
  • will also be used by your network engineers to maintain reachability between the different network segments.
  • will ease future network expansion and modification.

3. Does AFRINIC still have IPv4 resources?

Yes, AFRINIC still has a pool of public IPv4 addresses from which it issues to its members based on justified need. For more information, please consult the IPv4 Exhaustion Stats page.

4 How to develop one?

4.1 Things that you should know:

Public IP address: an IP address that is a globally unique routable IP address and usually used to connect to or provide service over Internet. 

Private IP address: Specific ranges reserved for private internets and usually used for corporate internal network . These ranges of IP addresses must be converted to public IP addresses through mechanisms like Network Address Translation (NAT) before the users can connect to the Internet (RFC1918, RFC4193)

Classless Inter-Domain Routing “CIDR” : A format used to describe IP address. It constitutes of two parts network part and the host part; for example 172.16.16.0/24. The CIDR notation specifies the IP address(172.16.16.0) and the associated routing prefix(/24).

How to calculate the routing prefix in CIDR notation:

Hosts bits >= log(no. of required IPs) [Approximate the next integer]

Network bits = 32 – hosts bits

Prefix size = /”Network bits”

Example: A network constitutes of 12 servers, 100 users in separate VLANs. The IT engineer wants to distribute the prefix 172.16.16.0/24 between the two VLANs. What is the network that will be given to each VLAN?

  • Determine the prefix size for each VLAN:
    • Servers VLAN:

hosts bits >= log12

>= 3.584

≈ 4

hosts bits = 4

network bits = 32 – 4 = 28

prefix size = /28

    • Users VLAN:

hosts bits >= log100

>= 6.644

≈ 7

hosts bits = 7

network bits = 32 – 7 = 25

prefix size = /25

The networks will be: 172.16.16.0/28 for servers VLAN and 172.16.16.128/25 for users VLAN.

4.2 Information you should have:

  • List of the intended services.
  • Number of devices on your network.
  • Number of Network/site (local or distributed/remote).
  • Statistics about users on the network (concurrent users).
  • Any available network topology diagram or architecture.
  • Any expected service growth/development plans.

4.3 Important Notes:

        Some of the sections below will refer to private IP addresses. Should these private IP addresses being NATed at your network, you must adjust the public IP addresses needs to cater for that. In fact, the private IP addresses have been mentioned in this document only because they are currently a network reality. It is believed that by eliminating NAT and moving towards IPv6, quality of services will enhance dramatically. 

        NAT aka Network Address Translation is one of the mechanisms used by network operators to compensate for the scarcity of IPv4 resources. In AFRINIC we discourage usage of NAT because it complicates the services provision, break the end-to-end communication model and hinder services evolution. We always encourage our members to get rid of NAT.

4.4 Getting to the real work: 

Use the questions below to fill in the table in each section where applicable as per network site.

1. You need to determine the requirements for your core network:

  • How many network nodes do you have?
  • Will the nodes be using public or private IP addresses?
  • Are your nodes connected using layer-2 device or layer-3 device or mix? If mix then determine number of nodes that will use layer-2 device and the ones that will use layer-3 device. If the nodes are connected directly to each other then consider it Layer-3 mode and calculate the number of connections instead of number of nodes.
  • Determine the IP addresses required per node depending on the connection mechanism. If it is L-2 then each network device will need “1” IP address. If it is L-3 then each network device will need “4” IP addresses.
  • If additional IP addresses is required for management then identify them.
  • The management IP addresses for network devices are usually public IP addresses that might or might not be reachable through the Internet. Add them to the public IP addresses per node.
  • Calculate the figures as follows:
    • Public IP addresses = no. of network nodes x public IP addresses per node
    • Private IP addresses = no. of network nodes x private IP addresses per node
Network nodes based on connection type Layer-3 connection Layer-2 connection
No. of nodes
No. private IP addresses per node
No. public IP addresses per node
Total private IP addresses
Private IP addresses in CIDR
Total public IP addresses
Public IP addresses in CIDR

 

2. You need to determine the requirements for your connections with the upstreams:

  • How many WAN connections do you have?

  • How many IP addresses are needed per WAN?

  • Usually WAN IP addresses will be supplied by your provider, is this your case?

  • Calculate the figures as follows:

    In case WAN IP addresses are not given by your provider then:

    Public IPs = no. of WAN connections x IPs per WAN

     

    No. of WAN connections
    IP addresses per WAN
    Total Public IP addresses
    Public IP addresses in CIDR

3. You need to determine the requirements for each service that will be provided:

  • How many servers per service?
  • How many IP addresses are needed per server (If you are using virtual servers, please include their requirements)?
  • Will the service be accessible from the Internet or will be restricted to your internal network? If yes, how many public IP is required per the server?
  • Calculate the figures as follows:
    • Total Private IP addresses = No. of servers * No. of IP addresses per server
    • Total Public IP addresses = No. of servers * No. of public IP addresses per server

 

Service List Service “1” ….... Service “n”
No. of servers
No. of IP addresses per server
Total private IP addresses
Private IP addresses in CIDR
Is it accessible from Internet
No. of public IP addresses per server
Total public IP addresses
Public IP addresses in CIDR

 

4. You need to determine the requirements for your end users (if applicable):

Classify your end users based on the provided services. If the end-user has more than one type of service then count it for each service separately. For each end-user category, answer the following questions.

  • How many IP addresses are required per end-user per category? If it is variable, what is the average number?
  • Is the service require use of public IP addresses? If yes, how many public IP addresses is required per end-user per category? Else set the public IP addresses number to zero.
  • How many end users per category ?
  • Calculate as follows:
    •  Total private IP addresses = IP addresses per end user x No. of end users
    • Total public IP addresses = public IP addresses per end user x No. of end users

 

Category List Category”1” …..... Category “n”
No. of IP addresses per end user
No. of end uses per category
No. of public IP addresses per end user
Total private IP addresses
Private IP addresses in CIDR
Total public IP addresses
Public IP addresses in CIDR

 

5. Go through your network, Is there any IP addresses requirements that doesn't fit in the previous mentioned groups? If yes then list them as follow:

  • No. of IP addresses required.
  • What is the type of required IP addresses? public or private?
  • Detailed description of the intended usage of these IP addresses.
  • Network diagram showing how they will fit with the other parts of your network.

6. Now that you have gathered the information, sum the total for each table and fill in the tables below:

  • The Private IP addresses requirements:
Network Segment Site “A” ….... Site “N”
Core Network
WAN connections
Services
Customers
Additional requirements
Total required IP addresses
Total IP addresses in CIDR

 

  • The Public IP addresses requirements:
Network Segment Site “A” ….... Site “N”
Core Network
WAN connections
Services
Customers
Additional requirements
Total required IP addresses
Total IP addresses in CIDR

       To comply with AFRINIC policies, you will be required to provide your IP addressing plan for both immediate and future need. The future period is specified in the current IP resources management policies. You can read more about these policies at www.afrinic.net.

       For any future plan repeat the same procedure taking into consideration the expected growth in each segment. You should be able to generate the same table to manifest your future requirements. The recommended format is to produce plans that shows immediate (0-3 months), medium term (6 months) and future (12 months). Such plans are more accurate and give better granularity which will be helpful in networks management and provision plans.

5 Practical example: 

            Company X is a service provider. It provides services like VPN, ADSL, Mobile broadband and dedicated Internet. The company has a customer base of 30,000 ADSL users, 500,000 mobile users and 1000 corporate users that use VPN. The VPN used private IP addresses only with average of 14 IP per user. At max 30% of the corporate customers have dedicated Internet in addition to VPN service, the average IP addresses assigned is 8. Some of the corporate customers prefer to use the uncommitted Internet services like ADSL and MB. Statistics during the peak hour showed that number of concurrent connected users during peak hours is 15,000 in the BRAS and 350,000 in the GGSN.

The recent market research conducted by company X marketing department shows the following:

- ADSL users are expected to grow in rate of 10% per year for the next 3 years.

- MB users will grow by 10%, 12%, 9% for the next three years respectively.

- Dedicated Internet users will decrease by 2% next year but grow at rate 5% per year after that.

- VPN users will increase at rate 7 - 8% for the coming three years.

           The network diagram below shows company X network. They have 3 main sites A, B and C. Each site contains two core routers and one router that serve as distribution layer. Each site contains one BRAS, one GGSN and corporate connections. Moreover, site C is connected to the company corporate network where the publicly accessible mail and web servers are hosted in addition to some internal services. DNS, Mail and website services are available in the Internet. The company use active-standby protection for each service. In addition, DNS service is constituted of 4 different servers.

The company currently using IP addresses from its upstream and implement techniques like PAT and NAT to be able to provide services. As part of a new business continuity strategy, they decided to request IP addresses from AFRINIC. They have been requested to submit IP addressing plan.

NW

Solution:

Following the procedure above, please find the below solution.

  • Core Network:

    There are 3 sites. Each site contains 3 routers, GGSN and BRAS which totals to 5 network nodes. They are connected using layer-3 and managed through private IP addresses. The 3 sites are symmetric, table below shows the requirements per one site.

    Network nodes based on connection type Layer-3 connection Layer-2 connection
    No. of nodes 5 N/A
    No. private IP addresses per node 0 N/A
    No. public IP addresses per node 4 N/A
    Total private IP addresses 0 N/A
    Private IP addresses in CIDR 0 N/A
    Total public IP addresses 20 N/A
    Public IP addresses in CIDR /27 N/A

 

  • WAN connections:

    The connections between the 3 sites are considered as WAN connections and will be use IP addresses from the requested prefix.

    No. of WAN connections 3
    IP addresses per WAN 4
    Total Public IP addresses 20
    Public IP addresses in CIDR /27

 

  • Services:

    Since active-standby mechanism is used, each server is actually two physical servers. Assuming VRRP is used, each server will need 3 different IP addresses.

    Service List ERP Mail Web DNS
    No. of servers 2 2 2 8
    No. of IP addresses per server 4 4 4 4
    Total private IP addresses 8 8 8 32
    Private IP addresses in CIDR /29 /29 /29 /27
    Is it accessible from Internet no yes yes yes
    No. of public IP addresses per server 0 3 3 3
    Total public IP addresses 0 6 6 24
    Public IP addresses in CIDR 0 /29 /29 /27

 

  • End-users:

    The end-users are categorised based on the service type; VPN, ADSL, Mobile Broadband “MB” and Direct Internet “DI”.

    Category List VPN ADSL MB DI
    No. of IP addresses per end user 14 1 1 8
    No. of end uses per category 1,000 30,000 500,000 300
    No. of public IP addresses per user 0 1 1 8
    Total private IP addresses 14,000 30,000 500,000 2,400
    Private IP addresses in CIDR /18 /17 /13 /20
    Total public IP addresses 0 30,000 500,000 2,400
    Public IP addresses in CIDR 0 /17 /13 /20

Summary:

  • The immediate IP addresses requirements as sum:
    Network Segment Private IP addresses Public IP addresses
    Core Network 0 60
    WAN connections 0 20
    Services 56 36
    Customers 546,400 532,400
    Additional requirements 0 0
    Total required IP addresses 546,456 532,516
    Total IP addresses in CIDR /13 /13

 

  • Taking into consideration the market research, the expected need of IP addresses in 12 months:
    Network Segment Private IP addresses Public IP addresses
    Core Network 0 60
    WAN connections 0 20
    Services 56 36
    Customers 600,402 585,352
    Additional requirements 0 0
    Total required IP addresses 600,458 585,468
    Total IP addresses in CIDR /12 /12

Following the same principles and based on the expected growth plan, the IP addressing could be adjusted to show both 6-months and 12-months future needs. Considering the 6-months and 12-months periods is advisable because it will give more accurate plans.