48 DUAL STACK CONFIGURATIONWhen configuring dual stack, go to these sections for information you areinterested in:■ “Dual Stack Overview” on page 691■ “Configuring Dual Stack” on page 691Dual Stack Overview Dual stack is the most direct approach to making IPv6 nodes compatible with IPv4nodes. The best way for an IPv6 node to be compatible with an IPv4 node is tomaintain a complete IPv4 stack. A network node that supports both IPv4 and IPv6is called a dual stack node. A dual stack node configured with an IPv4 address andan IPv6 address can have both IPv4 and IPv6 packets transmitted.For an upper layer application supporting both IPv4 and IPv6, either TCP or UDPcan be selected at the transport layer, while IPv6 stack is preferred at the networklayer. Figure 204 illustrates the IPv4/IPv6 dual stack in relation to the IPv4 stack.Figure 204 IPv4/IPv6 dual stack in relation to IPv4 stack (on Ethernet)Configuring DualStackYou must enable the IPv6 packet forwarding function before dual stack.Otherwise, the device cannot forward IPv6 packets even if IPv6 addresses areconfigured for interfaces.Follow these steps to configure dual stack on a gateway:IPv4 IPv6TCP UDPIPv4/IPv6 applicationEthernetProtocol ID:0x0800Protocol ID:0x86DDIPv4TCP UDPIPv4 applicationEthernetProtocol ID:0x0800IPv4 stack Dual stackTo do... Use the command... RemarksEnter system view system-view -Enable the IPv6 packet forwarding function ipv6 RequiredDisabled bydefault.
