Configuration guidelines
Follow these guidelines when you configure a tunnel interface:
Before configuring a tunnel interface on a switch, you may need create a service loopback group with its service type as Tunnel, and add unused Layer 2 Ethernet interfaces of the switch to the service loopback group.
On the switch, an encapsulated packet cannot be forwarded a second time at Layer 3 by using the destination address and routing table, but is sent to the loopback interface, which then sends the packet to the forwarding module for Layer 3 forwarding. You must reference a service loopback group on the tunnel interface. Otherwise, the tunnel interface will not be up and packets cannot be transmitted over the tunnel. For creation and configuration of a service loopback group, see Layer 2—LAN Switching Configuration Guide.
The tunnel bandwidth command does not change the actual bandwidth of the tunnel interface, but sets a bandwidth value for dynamical routing protocols to calculate the cost of a tunnel path. You can determine the value according to the bandwidth of the output interface.
You must configure a MTU no smaller than 1280 bytes for the tunnel (such as an IPv6 over IPv4 tunnel or an IPv6 over IPv6 tunnel).
By default, sending of ICMP destination unreachable packets is disabled. To enable it, use the ip unreachables enable command.