Chapter 16: Dynamic Routing Protocols
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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Figure 83:
Example of IS-IS and MT IS-IS Topologies
MT IS-IS Not Enabled
If MT IS-IS is not enabled, the best path from A to D is: A –> B –> C –> D
However, any IPv6 traffic from A –> D would be lost in Router B.
MT IS-IS Enabled
When MT IS-IS is enabled, two separate SPFs will run and maintain the two separate topologies, IPv4 and IPv6.
As a result:
The best IPv4 path from A to D is: A –> B –> C –> D
The best IPv6 path from A to D is: A –> E –> F –> C –> D
Adjacencies
Users need to know what they are running, IPv4 or IPv6, in order for the adjacency to be included in the correct topology.
If the interface only supports the IPv4 topology, the C4/c CMTS will not use the new MT TLV in the IS-IS Hello packet, and it
will not be advertised in the new TLV. Thus, the exclusion of MT TLV in the IIH implies that this interface is only part of the
IPv4 topology.
