Dynamic Host Configuration Protocol for IPv6 Prefix Delegation (DHCPv6 PD) is a mechanism that enables a network device to request a block of IPv6 addresses (a prefix) from an upstream router or DHCPv6 server. This delegated prefix can then be further distributed or assigned to devices within a local downstream network. PD is particularly useful for enabling hierarchical subnetting in scenarios involving routers with downstream interfaces, such as home gateways or mesh network border routers. The key benefit of PD is that it automates the process of obtaining address space, eliminating the need for manual configuration.
The XBee Hive for Wi-SUN includes support for DHCPv6 PD across multiple upstream and downstream interfaces.
By default, the Wi-SUN network is set up such that:
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The Ethernet and Wi-Fi interfaces are configured as upstream (WAN) interfaces, which use DHCPv6 to obtain an IPv6 address and PD from an upstream router.
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The Wi-SUN RF interface:
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is the primary downstream interface on the XBee Hive for Wi-SUN and always runs a DHCPv6 server to serve devices on the mesh network.
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uses a static and configurable IPv6 prefix, which defaults to
fd12::/64. If the user enables the "Use IPv6 Prefix Delegation" setting, the Wi-SUN RF interface will instead use a prefix obtained through PD from the upstream interface and the "Prefix ID" setting extends this prefix to create the final prefix assigned to the interface.
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The DHCPv6 server on the Wi-SUN RF interface is enabled and cannot be disabled, as it is required for the proper functioning of the mesh network.
Common prefix values
The following table summarizes the most common prefix lengths, the number of possible /64 subnets, and the valid range of Prefix ID values for a PD received from the upstream interface :
| Prefix Length | Number of /64 Subnets | Valid Prefix ID Range | Typical Use Case |
|---|---|---|---|
/48 |
65,536 |
0–65535 |
Large enterprise or advanced home networks |
/56 |
256 |
0–255 |
Medium-size business or ISP-provided PD block |
/60 |
16 |
0–15 |
Small business or advanced home setup |
/64 |
1 |
0 |
Single subnet for small networks |
Example PD scenarios
The following examples illustrate how prefix delegation works in different scenarios
