Curious why does IPv6 stops working if I restart my cable modem?

Installing and Using OpenWrt
1

I noticed that if I restart my cable modem all the devices stops using IPv6 until I reboot all the client interfaces. I am requesting a /56 and everything is working great until I reboot the modem, router stays on. I have Debian servers, AP using IPv6 and all stops working until I restart their interfaces. What is the reason behind this?

2

Does the cable company assign you a different prefix when it reconnects?

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3

No, same prefix

4

Maybe in the future someone who is an IPv6 expert can figure out why the downstream devices (AP) and clients loose IPv6 connectivity after a modem reboot, maybe RA service stops working.

5

I created a bash script to solve the problem of IPv6 stop working. On my access point I created lan6 interface to request from upstream router and a br-guest for guest wifi. If IPv6 is not detected in br-guest then lan6 interface is restarted.

#!/bin/sh
IPv6Connectivity=$(/sbin/ip -6 addr show dev br-guest | grep inet6 | awk -F '[ \t]+|/' '{print $3}' | grep '^2')
if [[ -z "$IPv6Connectivity" ]]; then
logger "ALERT: Guest IPv6 connectivity lost, restarting interface"
ifdown lan6 && ifup lan6
fi
exit 0

Chmod the script
chmod +x /root/IPv6Connectivity.sh
Cron Job every 3 hours.
0 */3 * * * /bin/sh /root/IPv6Connectivity.sh

This is a private fix, hopefully someone can figure out why SLAAC stops working after upstream router reboot and find a permanent fix.

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