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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Originating OSPFv3 interface and router.
Instance ID and interface ID.
Hello interval.
Optional capabilities of the originating router.
Hello packets also include a list of router IDs for the routers that the originating interface has communicated with. If the
receiving interface sees its own router ID in this list, then bidirectional communication has been established between the
two interfaces.
Keepalive Message
OSPFv3 uses Hello packets as a "keepalive" message to determine if a neighbor is still communicating. If a router does not
receive a Hello packet by the configured dead interval (usually a multiple of the Hello interval), then the neighbor is
removed from the local neighbor table.
Fast Hello Packets for OSPFv2 and v3
Both OSPV2 and OSPFv3 support Fast Hello Pa ckets in the C4/ c CMTS implementation. Operators can configure the sendi ng of Hello pa ckets in intervals of less tha n one second. S uch a configuration will result in faster converge nce in a n OSPF netw ork.
Interval Settings
Setting the dead interval to one second will turn on the Fast Hello feature with the default value of 5 for the Hello
multiplier (200 ms Hello interval). The Hello multiplier is not configurable for OSPFv3.
Equal Cost Multipath
Routing protocols can use equal cost multipath (ECMP) to share traffic across multiple paths. When a router learns
multiple routes to a specific network, it installs the route with the lowest administrative distance in the routing table.
If the router receives and installs multiple paths with the same administrative distance and cost to a destination, ECMP can
occur.
Path Number Limit
The number of paths used is limited by the number of entries that the routing protocol puts in the routing table. The C4/c
CMTS supports up to a maximum of four equal cost routes.
