Chapter 23: IPv6
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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multicast (specifically an all-nodes link-local multicast). In addition, an IPv6 address has a notion of forwarding scope where
node-local, link-local, site-local, and global scopes are defined. In IPv6, scope is encoded as part of the prefix and nodes are
not permitted to forward link-local packets beyond their scope. In IPv4, scope was imprecisely defined by small TTL values,
however in IPv6, scope is precisely defined and enforced. In particular, IPv6 scope enforcement applies to both source and
destination IPv6 addresses.
Table 91.
IPv6 Address Ranges and Scope
Address Range(s)
Scope
2000::/3
Global scope unicast addresses
FEC0::/10 FC00::/8, and FD00::/8
Site-local scope unicast addresses
FE80::/10
Link-local scope unicast addresses
Interface Assignment
In IPv6, addresses are assigned to interfaces, not to nodes. A single interface may be assigned any number of IPv6
addresses of any kind. The C4/c CMTS supports the assignment of only one link-local scope address to each physical
interface. This address is typically assigned automatically and is unique over all interfaces in the C4/c CMTS.
IPv6 multicast addresses are taken from the FF00::/8 address space and include an explicit scope indicator in bits 12-15.
Thus, IPv6 multicast addresses are of the form FF0x::/16 where x is the multicast scope indicator (encoded as 1 for node-
local, 2 for link-local, 5 for site-local, and E for global scope).
Note: Anycast addresses are not supported.
There are two special addresses in IPv6:
1.
The unspecified address has the value 0:0:0:0:0:0:0:0 (or ::), and is more or less equivalent to 0.0.0.0 in IPv4. It cannot
be used as a destination address and is only used as a source address when a new address is assigned to a link and is
being tested by duplicate address detection (DAD).
The address ::/0 is typically used as part of the default route statement.