33.1.4 ISATAP Tunnel
Intra-site Automatic Tunnel Addressing Protocol (ISATAP) is an IPv6 tunnel technology by
which an intra-site IPv6 architecture takes an IPv4 network as one nonbroadcast
multi-access (NBMA) link layer, namely taking an IPv4 network as the virtual link layer of the
IPv6.
ISATAP is applicable when the pure IPv6 network inside a site is not ready for use and IPv6
packets need be transferred internally in the site. For example, a few of IPv6 hosts for test
need communicate with each other inside the site. Through the ISATAP tunnel, the
IPv4/IPv6 dual stack hosts on a same virtual link can communicate with each other inside
the site.
On the ISATAP site, the ISATAP router provides standard router advertisement packet,
allowing automatic configuration of the ISATAP host inside the site. At the same time, the
ISATAP router performs the function that an intra-site ISATAP host and external IPv6 host
forward packets.
The IPv6 address prefix used by ISATAP can be any legal 64-bit prefix for IPv6 unicast,
including the global address prefix, link local prefix and site local prefix. The IPv4 address is
placed as the ending 32 bits of the IPv6 address, allowing a tunnel to be automatically built.
It is very possible that ISATAP is used with other transition technologies. Especially when
used with the 6to4 tunnel technology, it can make the dual stack host of an internal network
access an IPv6 backbone network very easily.
ISATAP interface identifier
The unicast address used by ISATAP is in the form of a 64-bit IPv6 prefix plus a 64-bit
interface identifier. The 64-bit interface identifier is generated in the revised EUI-64 address
form. The value of the first 32 bits of the interface identifier is 0000:5EFE, indidcating that it
is an interface identifier of ISATAP.
ISATAP address structure
An ISATAP address refers to the unicast address containing an ISATAP interface identifier in
its interface identifier. TheISATAP address structure is shown in the following figure:
Figure 33-3
To Next Page
Loading...
Need help?
General