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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Operational Concerns
It is important that Prefix-Stability is configured correctly in order to see the expected results. The following are some
possible configuration errors:
If one of the participating C4/c CMTSs is not configured to redistribute PD routes and yet a commercial customer was
moved from or to this C4/c CMTS, then the two C4/c CMTSs will not detect the collision. The collision can be detected
only by IGP protocol packets generated as result of redistributing the PD routes. Make sure the participating C4/c
CMTSs are configured to redistribute the PDs that are expected to move.
Make sure all participating C4/c CMTSs are redistributing the PDs into the IGP using the same metric type (i.e. Internal
or External Metric type in IS-IS and External Type 1 or External Type 2 in OSPF) and the same metric value. Different
metric values or different metric types in participating C4/c CMTSs would alter the IGP protocol’s processing logic and
hence IGPs would behave differently (as far as their route selection criteria is concerned). This would impact the
detection of route collisions. Participating C4/c CMTSs are those that expect to see a set of commercial customers
moved among them.
Make sure that the address ranges for commercial and residential customers are different and non- overlapping. If
these address ranges are mixed or overlapping, there will be unexpected collisions. Whenever collisions are detected,
the C4/c CMTSs check to see if the modem is online or offline and accordingly keep or delete the PD route. Bad
configurations can result in the deletion of routes incorrectly if the modems in question happen to be offline at that
time.
The OSPF area type must be either Regular or NSSA. Other area types will not be able to process the Type 5 or Type 7
LSAs that are generated by OSPF when PD routes are redistributed; as a result, route collision detection will not work.
The IS-IS Node type must be either L1 or L2. The IS-IS Node Type L1L2 is not supported for use with Prefix Stability.
Such a configuration would generate an excessive amount of TLVs for all C4/c CMTSs to process.
The
DOCSIS MULPI Specification, version 3.0
(see CableLabs Specifications--DOCSIS 3.0 -
http://www.cablelabs.com/specs/specification-search/?cat=docsis&scat=docsis-3-0
) contains a description of this feature.
The C4/c CMTS implements this feature using IPv6 distribute lists and route snooping. It is expected that MSOs will use
route snooping primarily for commercial customers who must maintain the same leased IPv6 prefix when there are node
splits. IPv6 distribute lists will be used to aggregate PDRI routes for all other customers.
IPv6 Prefix Stability is enabled by default. To disable this feature use the following command:
configure ipv6 prefix-stability no