ipv6: Neighbour table overflow

One of my virtual machines hosted at Gandi had an excessive amount of error messages

localhost kernel: ipv6: Neighbour table overflow.

The cause of this error message are the IPv6 router announcements that try to discover and configure the IPv6 neighbourhood. The excessive amount of messages were polluting the logs.

After contacting the Gandi helpdesk they provided insight on the cause of the error message and provided mitigations to prevent these type of errors. I had to update /etc/sysctl.conf with these entries

# Force gc to clean-up quickly
net.ipv4.neigh.default.gc_interval = 3600
net.ipv6.neigh.default.gc_interval = 3600
 
# Set ARP cache entry timeout
net.ipv4.neigh.default.gc_stale_time = 3600
net.ipv6.neigh.default.gc_stale_time = 3600
 
# Setup DNS threshold for arp 
net.ipv4.neigh.default.gc_thresh3 = 8192
net.ipv4.neigh.default.gc_thresh2 = 4096
net.ipv4.neigh.default.gc_thresh1 = 2048

net.ipv6.neigh.default.gc_thresh3 = 8192
net.ipv6.neigh.default.gc_thresh2 = 4096
net.ipv6.neigh.default.gc_thresh1 = 2048

The configuration file sysctl.conf is a file containing the setting that reads and modifies the attributes of the system kernel.

After updating the configuration file, had to apply them with

sysctl -p

Changing the configuration file and applying the settings prevented these error messages from polluting the syslog messages.

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