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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The following guidelines apply to CPEs using IPv6 link-local addresses:
A CPE can have only one link-local address.
CPEs are not required to use EUI-64 address formatting for link-local addresses, but CMs are. If a CPE or CM uses EUI-
64 in its SIPv6 link-local address, the SMAC of packets must match its MAC address in packets it sends. (EUI-64 is
trademarked by the IEEE. “EUI” stands for “Extended Unique Identifier”.)
The C4/c CMTS verifies that a link-local address being used by a cable-side host (CM or CPE) is not being used by any
other cable-side host.
Reverse-path verify does not apply to link-local addresses.
IPv6 link-local addresses are not subject to DHCP host validation.
The C4/c CMTS supports Proxy Duplicate Address Detection (DAD), which ensures the IPv6 addresses are unique across
all cable interfaces. IPv6 Proxy DAD applies to link-local, site-local, and global addresses.
Caution: If an IPv6 site-local or global address on a cable interface is changed or removed or prefix length on a cable
interface is changed, then be well aware that all cable modems on that prefix will be reset and CPEs using an address
based on that IPv6 prefix will be stranded until they DHCP to acquire a new IPv6 address.
No communication with the cable modems or CPEs that use site-local or global IP addresses based on the removed IPv6
prefix is possible until the cable modems and CPEs DHCP to acquire a different IPv6 address on a prefix of that interface.
Note: It is recommended that when an IPv6 site-local/global address or prefix length is modified or removed from a cable
interface, all IPv6 cable modems on that prefix be reset.
Neighbor Discovery Proxy for CPE Traffic
The C4/c CMTS does not bridge or support Neighbor Discovery proxy for CPE traffic on the same prefix for CPEs behind
different modems. In order for IPv6 global and site-local traffic on the same prefix to be forwarded by the C4/c CMTS, the
traffic must be routed through the C4/c CMTS. This is accomplished by explicitly advertising the cable interface prefixes in
question as off-link. The off-link qualifier is applied to the entire prefix.
Below is an example for assigning an IPv6 site-local address to a cable interface and then assigning the off-link qualifier to
its corresponding prefix. The prefix specified by this command will be advertised in solicited and periodic ICMPv6 Router
Advertisement messages sent from the C4/c CMTS. When a device on the cable interface receives a Router Advertisement
with an off-link prefix, it then forwards all packets with this prefix as the destination to the C4/c CMTS acting as a router.