of Host B. For the source IPv4 address in the encapsulating IPv4 header, IPv4 on Host A determines the best source IPv4 address to use to reach the destination IPv4 address

192.168.41.30. In this case, Host A has only a single IPv4 address assigned, so IPv4 on Host A uses the source address of 10.40.1.29.

ISATAP Components

An ISATAP deployment consists of ISATAP hosts, ISATAP routers, and one or more logical ISATAP subnets. Figure 12-2 shows the components of an IPv4-capable intranet that is using ISATAP and a single ISATAP subnet.

Logical ISATAP Subnet

(IPv6 over IPv4 Traffic)

ISATAP Host

Figure 12-2 Components of ISATAP

The IPv4-only portion of the intranet is the ISATAP subnet. The IPv6-capable portion of the intranet has native IPv6 routers and addressing. Hosts on the IPv6-capable portion of the intranet are configured with global or unique local addresses on their LAN interfaces and do not need to use IPv4 encapsulation to communicate with each other using IPv6.

ISATAP hosts have an ISATAP tunneling interface and perform their own tunneling to other ISATAP hosts on the same ISATAP subnet (host-to-host tunneling) or to an ISATAP router (host-to-router tunneling). ISATAP hosts can use global, unique local, or link-local ISATAP addresses to communicate with each other. To communicate with other ISATAP hosts on the ISATAP subnet using their ISATAP global, unique local, or link-local addresses, ISATAP hosts tunnel their packets directly to each other. To communicate with IPv6 hosts on the IPv6-capable portion of the intranet using their native global or unique local addresses, ISATAP hosts tunnel their packets to an ISATAP router.