Example IPv6 Topology and Prefix-NAT Configuration

Due to the nature of the IPv6 address scheme, the following scenario presents a simplistic approach. According to IANA, the LIR/RIR address assignment should be /48 for subscribers (including private housing). This enables each subscriber to configure about 216 networks. These numbers are immense, so the scenario uses a simple address scheme based on IPv6 subnetting.

Consider the following scenario, which is shown in Figure 12 - Example LinkProof IPv6 Topology:

LinkProof is connected to the following two IPv6 service providers:

—	ISP A dedicates the following public addresses: 2030:2020:1000::/48

—	ISP B dedicates the following public addresses: 2040:1020:2000::/52

The network administrator has followed IANA recommendations and has subnetted the internal network using ULA.

In addition, the network administrator has subnetted the external routers accordingly.

Example LinkProof IPv6 Topology

Notes

>>	The use of the /55 prefix to subnet the /48 network is arbitrary. In real life, subnetting will usually be based on the need for free networks as well as the existing topology.

>>

The Prefix-NAT feature supports network ranges from /64 to /48.Prefix NAT is allowed as long as the number of internal IPv6 address is smaller than or equal to the number of external IPv6 addresses. So, for example, when the external router is configured with a /64 range, using a ULA /48 for Prefix-NAT is not allowed. When the public IPv6 address range of the external router is /59, using a ULA /59 for Prefix-NAT is allowed.

>>	The translation is done per address. So, for example, an IPv6 ULA address with the address fc00:1002:fc01:3000:2000::1001/48 will be translated on the external interface using 2030:2020:1000::/48 as 2030:2020:1000:3000:2000::1001.

>>	The routers are all defined in a single router farm.

>>	The routers are all set as active, although it is not necessary for the functionality of the Prefix-NAT feature.

Table 89 - Router Definitions for Example IPv6 Topology, page 149 lists the router definitions based on the example topology shown in Figure 12 - Example LinkProof IPv6 Topology and Table 88 - LinkProof Interface Definitions for Example IPv6 Topology, page 149.

 

LinkProof Interface Definitions for Example IPv6 Topology

Role	IP Address	Prefix Length	IF	VLAN Tag	Status	Peer IP Address	Preferred Lifetime and Valid Lifetime
ISP B	2030:1020:2000:a0::1001	59	G-11	0	Preferred	::	Infinite
ISP A	2030:2020:1000:200::1001	55	G-5	0	Preferred	::	Infinite
Internal LAN	fc00:1002:fc01:3000:2000::1001	59	G-2	0	Preferred	::	Infinite

 

Router Definitions for Example IPv6 Topology

Router Name	IP Address	OperStatus	Weight	Farm Name
ISP A	2030:2020:1000:200::1000	Active	1	IPv6Routers
ISP B	2030:1020:2000:a0::1000	Active	1	IPv6Routers

Figure 13 - Configuration of Example Static Prefix-NAT Entry in WBM and Figure 14 - Example Static Prefix-NAT Table in WBM show the following Static Prefix-NAT configuration in Web Based Management:

The entire /59 ULA will be replaced when accessing the IPv6 Internet using ISP A.

The range of ULA starting from ::1001 ending with 2001 will be replaced with the prefix of ISP B when accessing the IPv6 Internet.

Configuration of Example Static Prefix-NAT Entry in WBM

Example Static Prefix-NAT Table in WBM