14-1 
14  Dual Stack Configuration 
When configuring dual stack, go to these sections for information you are interested in: 
z  Dual Stack Overview 
z  Configuring Dual Stack 
Dual Stack Overview 
Dual stack is the most direct approach to making IPv6 nodes compatible with IPv4 nodes. The best 
way for an IPv6 node to be compatible with an IPv4 node is to maintain a complete IPv4 stack. A 
network node that supports both IPv4 and IPv6 is called a dual stack node. A dual stack node 
configured with an IPv4 address and an IPv6 address can have both IPv4 and IPv6 packets 
transmitted. 
For an upper layer application supporting both IPv4 and IPv6, either TCP or UDP can be selected at 
the transport layer, while IPv6 stack is preferred at the network layer.   
Figure 14-1 illustrates the IPv4/IPv6 dual stack in relation to the IPv4 stack. 
Figure 14-1 IPv4/IPv6 dual stack in relation to IPv4 stack (on Ethernet) 
IPv4 application IPv4/IPv6 application
TCP UDP TCP UDP
IPv4 IPv4 IPv6
Ethernet Ethernet
Protocol ID:
0x0800
Protocol ID:
0x0800
Protocol ID:
0x86DD
IPv4 stack Dual stack
 
 
Configuring Dual Stack 
You must enable the IPv6 packet forwarding function before dual stack. Otherwise, the device cannot 
forward IPv6 packets even if IPv6 addresses are configured for interfaces. 
Follow these steps to configure dual stack on a gateway: 
To do…  Use the command…  Remarks 
Enter system view  system-view  — 
Enable the IPv6 packet forwarding function  ipv6 
Required 
Disabled by 
default.