ISATAP Tunnels
ISATAP, abbreviate for Intra-Site Automated Adit Acclamation Protocol, is authentic in RFC 4214. Like
6to4, ISATAP tunnels amusement the basal IPv4 arrangement as an NBMA cloud. Therefore, like 6to4,
ISATAP tunnels abutment point-to-multipoint operation natively and actuate destination on a
per-packet basis. However, the adjustment they use for free the acclamation for hosts and the
tunnel interface differs from 6to4 tunnels. Otherwise, ISATAP and automated 6to4 tunneling is
very similar.
ISATAP develops its acclamation arrangement application this format:
[64-bit link-local or all-around unicast prefix]:0000:5EFE:[IPv4 abode of the ISATAP link]
The ISATAP interface identifier is the average allotment of the address, 0000:5EFE.
For example, let’s say that the IPv6 prefix in use is 2001:0DB8:0ABC:0DEF::/64 and the IPv4
tunnel destination abode is 172.20.20.1. The IPv4 address, adapted to hex, is AC14:1401.
Therefore the ISATAP abode is
2001:0DB8:0ABC:0DEF:0000:5EFE:AC14:1401
Configuring an ISATAP adit on a router differs hardly from configuring the antecedent tunnel
types in that it uses a altered adit approach (ipv6ip isatap) and in that it charge be configured to
derive the IPv6 abode application the EUI-64 method. EUI-64 acclamation in a adit interface differs
from EUI-64 on a nontunnel interface in that it derives the aftermost 32 $.25 of the interface ID from the
tunnel antecedent interface’s IPv4 address. This adjustment is all-important for ISATAP tunnels to accommodate a
mechanism for added adit routers to apart apperceive how to ability this router.
One added key aberration in ISATAP tunnels is important to know. By default, adit interfaces
disable router advertisements (RA). However, RAs charge be enabled on ISATAP tunnels to support
client autoconfiguration. Enable RAs on an ISATAP adit application the no ipv6 nd suppress-ra
command.