# Configure IPv6 in IPv4 Tunnel

To enable isolated IPv6 hosts and networks to reach each other over an existing IPv4 network infrastructure, you can configure an IPv4-in-IPv6 tunnel. At the tunnel head end, IPv6 packets are encapsulated into IPv4 packets and sent to the remote tunnel destination. At the destination, the IPv4 packet headers are stripped and the original IPv6 packets are forwarded into the IPv6 cloud.

Until the IPv4 and IPv6 protocols are able to run on the same network infrastructure using dual-stack technology, a transitional mechanism such IPv4in-IPv6 tunnelling is required to facilitate communication.

Note: Similar to Port Forwarding, this feature is not available in a server-only configuration. It is only available when the server is operating in server-gateway mode.

## Preconditions

- The IPv4 address of the remote endpoint must be reachable via ICMP (Internet Control Message Protocol).

- If you are behind a firewall, please make sure it allows passage of Internet Protocol 41. This protocol is contained in the IPv4 header and indicates that an IPv6 packet is encapsulated within the IPv4 packet.

To configure an IPv4-in-IPv6 tunnel:

1. Under Configuration, click IPv6-inIPv4.

2. Configure the settings as required and then click Save:

Setting | Description
--- | ---
IPv4 Address of the Remote End | Enter the IPv4 address of tunnel destination. This address must be routable on the IPv4 network. Typically, it is the external interface of the router located at the destination.
IPv6 Address of the Tunnel (Optional) | If the MSL server is functioning as a gateway to the internet, you can configure its external tunnel interface with an IPv6 address. This enables the interface to be addressable by IPv6 traffic. You may configure only one address on this interface. If this field is left blank, no address will be assigned to the external tunnel interface on the MSL server. Note: Your service provider provides this IPv6 address.
IPv6 Networks | Enter one or more IPv6 network addresses for the destination. Based on these entries, the system creates a routing table that defines the ultimate destination of the IPv6 packets that are being tunneled. You can enter a single address or a block of addresses (specified by writing a slash (/) followed by a number which defines the length of the network prefix in bits). Use commas to separate multiple entries.