Configuring 6to4 Tunnel 709n For the configuration of the MTU of IPv6 packets sent over a tunnel interface, referto the ipv6 mtu command in “Configuring the Interface MTU” on page 670.c CAUTION:■ Only one automatic tunnel can be configured at the same tunnel source.■ No destination address needs to be configured for an automatic tunnelbecause the destination address can automatically be obtained from the IPv4address embedded in the IPv4-compatible IPv6 address.■ If the addresses of the tunnel interfaces at the two ends of a tunnel are not inthe same subnet, a forwarding route through the tunnel to the peer must beconfigured so that the encapsulated packet can be forwarded normally. Youcan configure static or dynamic routes. For the detailed configuration, refer to“Static Routing and Dynamic Routing” on page 817.■ The automatic tunnel interfaces encapsulated with the same protocol cannotshare the same source IP address.■ Automatic tunnels do not support dynamic routing.■ When you configure a static route, you need to configure a route to thedestination address (the destination IP address of the packet, instead of theIPv4 address of the tunnel destination) and set the next-hop to the tunnelinterface number or network address at the local end of the tunnel. Such aroute must be configured at both ends of the tunnel.Configuration Example 1 Network requirementsIsolated IPv6 networks are interconnected through a 6to4 tunnel established in theIPv4 network.Network diagramFigure 213 Network diagram for a 6to4 tunnelConfiguration procedureThe following example shows how to configure a 6to4 tunnel between borderrouters on isolated IPv6 networks. After the IPv4 address 2.1.1.1 is converted intoan IPv6 address, the address prefix is 2002:0201:0101::/64. The configured staticroute directs all traffic destined for the IPv6 address with the prefix 2002::/16 tothe tunnel interface of the 6to4 tunnel.■ Configuration on Router A.Eth1/02.1 .1.1/24Eth1 /05.1.1 .1/24Eth1/12002:0201 :0101 :1::1/64Eth1/12002 :0501 :0101 :1::1/64Router A Router B6to4 router 6to4 routerHost A2002:0201 :0101 :1::2/64Host B2002 :0501:0101 :1 ::2/64IPv4 netwok
