Users Guide

Layer 3 Routing Commands 1570
ipv6 nd nud retry
This command configures the exponential backoff multiple to be used in the
calculation of the next timeout value for Neighbor Solicitation transmission
during NUD (neighbor unreachability detection) following the exponential
backoff algorithm. Use the no form of the command to return the backoff
multiple to the default.
Syntax
ipv6 nd nud retry backoff-multiple
no ipv6 nd nud retry
• backoff-multiple—The value ranges from 1 to 5. The next timeout value is
clamped at a maximum value of 60 seconds if the result of the exponential
back-off calculation is greater than 60 seconds.
Default Configuration
The default exponent is 1.
Command Mode
Global Configuration
User Guidelines
Once the neighbor is resolved and added in the hardware, traffic is
continuously forwarded by the router using neighbor entry. The neighbor
entry in the cache transitions to the STALE state after the effective STALE
timeout value (a random value between 15 and 45 seconds per RFC 2461).
To bridge the gap between the neighbor discovery state and the neighbor
cache state, the application periodically iterates through the STALE entries
and triggers NUD on those entries to detect any address/station movements
or MAC address changes.
When NUD is triggered, neighbor solicitation PROBE packets (unicast and
multicast) are sent periodically, separated by exponential binary values
instead of the normal 1 second interval. This ensures that when the network
(not just our router but more routers in the network) is congested, the NUD
process for the existing STALE entries takes enough time before ultimately
removing the cache entry through garbage collection. Without the