IPv6 Addressing Plan for Singlehomed Enterprise Networks

Before you start it is recommended to go through the article first: IPv6 Subnetting

Also, you may also consider reading IP Addressing Plan for ISP

Basic Considerations:

  • The enterprise is singlehomed (i.e. it has only one upstream/service provider)
  • It is not a RIR member (i.e. it does not have own IP address)

Let’s say, your enterprise received a /48 v6 prefix (2001:DB8:12::/48) from your upstream.

  1. Subnet the whole /48 prefix into /56 which will give you 2^8=256 /56 subnets. If you allocate the first /56 for your infrastructure, you still have 255 /56 subnets to allocate per building or per department as you wish.
  2. Take the first /56 (2001:DB8:12::/56) for Infrastructure and p2p peering and distribute it according to the following plan.
    1. First /64 (2001:DB8:12::/64): Loopback IP (Configure as /128 per node). This way you can keep the length of loopback address smaller :-). I prefer not to use the first address since :: looks a weird to me but it’s definitely usable. Instead, I start with the ::1 which more like the loopback of my first device and it makes me more comfortable.
      Example:

      • Node 1’s Loopback: 2001:DB8:12::1/128
      • Node 2’s Loopback: 2001:DB8:12::2/128
      • Node 3’s Loopback: 2001:DB8:12::3/128
        so on and so forth…
    2. Second /64 (2001:DB8:12:1::/64) is for Management IP.
      Example:

      • Node 1’s Management IP: 2001:DB8:12:1::1/64
      • Node 2’s Management IP: 2001:DB8:12:1::2/64
      • Node 3’s Management IP: 2001:DB8:12:1::3/64
        so on and so forth…
    3. From third /64 (2001:DB8:0:2::/64) and onwards: Backbone P2P peering. Though IPv6 protocol design expectation is to use /64 per subnet/P2P link, RFC6164 recommends to use /127 (reserve /64 for the link, but configure as /127)
      Example:

      • 1st backbone P2P Peering: 2001:DB8:12:2::/64 (Node A’s interface IP: 2001:DB8:12:2::/127 and Node B’s interface IP: 2001:DB8:12:2::1/127)
      • 2nd backbone P2P Peering: 2001:DB8:12:3::/64 (Node A’s interface IP: 2001:DB8:12:3::/127 and Node B’s interface IP: 2001:DB8:12:3::1/127)
      • 3rd backbone P2P Peering: 2001:DB8:12:4::/64 (Node A’s interface IP: 2001:DB8:12:4::/127 and Node B’s interface IP: 2001:DB8:12:4::1/127)
        so on and so forth…
    4. You can go up to 2001:DB8:12:FF::/64
  3. Right from the second /56 (2001:DB8:12:100:/56) start allocating each /56 to each building or each department based on you network design. This way, each Building or department can have 2^8=256 /64 subnets.
    Example:

    • Building 1 (or Department 1) : 2001:DB8:12:100::/56
    • Building 2 (or Department 2) : 2001:DB8:12:200::/56
    • Building 3 (or Department 3) : 2001:DB8:12:300::/56
      so on and so forth… up to 2001:DB8:12:FF00::/56
  4. From the per building (or department) allocation, you can have one /64 subnet per VLAN or LAN.
    Example:

    • Building 1 VLAN 1: 2001:DB8:12:100::/64
    • Building 1 VLAN 2: 2001:DB8:12:101::/64
    • Building 1 VLAN 3: 2001:DB8:12:102::/64
  5. For building 2:
    Example:

    • Building 2 VLAN 1: 2001:DB8:12:200::/64
    • Building 2 VLAN 2: 2001:DB8:12:201::/64
    • Building 2 VLAN 3: 2001:DB8:12:202::/64
    1. so on and so forth…

This way you can have a scalable IPv6 address planning for your enterprise network.

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