Information Technology Reference
In-Depth Information
Site C
IPv4 and IPv6
Site A
IPv4 only
Dual-Stack Backbone
IPv4 and IPv6
Site B
IPv4 and
IPv6
Site D
IPv4 and IPv6
Figure 9-13
Dual-Stack Network Address Translation-Protocol Translation
Hybrid Model
The hybrid model uses a combination of transition mechanisms. The transition mecha-
nisms used are based on multiple network criteria such as number of hosts, IPv6 capable
hardware, and location of IPv6 services. The hybrid model uses a combination of transi-
tion mechanisms:
Dual-stack mechanism
■
ISATAP
■
Manually configured tunnels
■
The hybrid model can be used to tunnel a dual-stack host on an IPv4 access layer to an
IPv6 core. As shown in Figure 9-14, the dual-stack computer establishes an ISATAP tunnel
to the core layer to access services from the dual-stack server on the right.
Another scenario is to tunnel dual-stack distribution layers over an IPv4-only core. As
shown in Figure 9-15, the dual-stack computer on the left can access the dual-stack server
on the right via the manually configured tunnels. Multiple tunnels are configured to pro-
vide redundancy and load balancing.
Service Block Model
In the service block model, a centralized layer that services dual-stack devices is created
with tunnels manually configured between the distribution layer and the service block.
Dual-stack hosts also connect via ISATAP tunnels. In Figure 9-16, the dual-stack client on
the left connects to the service block to establish connectivity with the dual-stack server
on the right.
