Configuring System Information 123Defining IPv6 ISATAP TunnelsThe IPv6 ISATAP Tunnel Page defines the tunneling process on the device, which encapsulatesIPv6 packets in IPv4 packets for delivery across an IPv4 network.The Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) is an IPv6 transition mechanism which isdefined as a tunneling IPv6 interface and is meant to transmit IPv6 packets between dual-stack nodes ontop of an IPv4 network.When enabling ISATAP on a tunnel interface, an explicit IP address is configured as the tunnel source oran automatic mode exists where the lowest IPv4 address is assigned to an IP interface. This source IPv4 isused for setting the tunnel interface identifier according to ISATAP addressing convention. When atunnel interface is enabled for ISATAP, the tunnel source must be set for the interface in order for theinterface to become active.An ISATAP address is represented using the [64-bit prefix]:0:5EFE:w.x.y.z, where 5EFE is the ISATAPidentifier and w.x.y.z is a public or private IPv4 address. Thus, a Link Local address will be represented asFE80::5EFE:w.x.y.zOnce the last IPv4 address is removed from the interface, the ISATAP IP interface state becomes inactiveand is represented as “Down”, however the Admin state remains enabled.When defining tunneling, note the following:• An IPv6 Link Local address is assigned to the ISATAP interface. The initial IP address is assigned to theinterface, and the interface state becomes Active.• If an ISATAP interface is active, the ISATAP router IPv4 address is resolved via DNS by usingISATAP-to-IPv4 mapping. If the ISATAP DNS record is not resolved, the ISATAP hostname-to-address mapping is searched in the host name cache.• When an ISATAP router IPv4 address is not resolved via DNS process, the status of the ISATAP IPinterface remains Active. The system does not have a default gateway for ISATAP traffic until the DNSprocedure is resolved.• In order for an ISATAP Tunnel to work properly over an IPv4 network, an ISATAP Router is required tobe set up.To open the IPv6 ISATAP Tunnel page, click System→ IP Addressing→ IPv6 ISATAP Tunnel in the treeview.
