Fortigate PPPOE IPv6 , client PC cannot connect internet using ipv6 when pppoe redial

[AntonyChen]

Dear everyone.
I have configured my network to use Ipv6 as detail below, it work ok, this configure allow client pc connected to LAN interface can connect to internet using ipv6 OK with ipv6 from DHCP6 server.
But the problem is if the pppoe is reconnect, IPv6 Address/Prefix on LAN interface will changed because it is delegated to WAN1 and the ISP provide dynamic IP
The DHCPv6 will assign a new ipv6 to computer network, now the computer may contain multiple ip address, the previous IP and the new ip. But after this, the PC cannot connected to internet using ipv6, i have to disable the network interface and enable again or reconnect to wifi network to make the PC work with new Ipv6

I think that there are sth wrong or miss in my configuration, so pls kindly help

Thanks

config system interface
edit "wan1"
set vdom "root"
set mode pppoe
set allowaccess ping https http fgfm
set type physical
set explicit-web-proxy enable
set role wan
set snmp-index 1
config ipv6
set ip6-mode pppoe
set ip6-allowaccess ping https http
set dhcp6-prefix-delegation enable
set autoconf enable
config dhcp6-iapd-list
edit 1
set prefix-hint ::/60
next
end
end
set username "xxxx"
set password ENC XXXX
set dns-server-override disable
next
end





config system interface
edit "LAN"
set vdom "root"
set ip 192.168.1.1 255.255.255.0
set allowaccess ping https ssh http fgfm fabric ftm speed-test
set type hard-switch
set explicit-web-proxy enable
set device-identification enable
set role lan
set snmp-index 7
config ipv6
set ip6-mode delegated
set ip6-allowaccess ping https
set ip6-send-adv enable
set ip6-manage-flag enable
set ip6-other-flag enable
set ip6-delegated-prefix-iaid 1
set ip6-upstream-interface "wan1"
set ip6-subnet ::1/64
config ip6-delegated-prefix-list
edit 1
set upstream-interface "wan1"
set delegated-prefix-iaid 1
set subnet ::/64
next
end
end
next
end



config system dhcp6 server
edit 1
set interface "LAN"
set upstream-interface "wan1"
set delegated-prefix-iaid 1
set ip-mode delegated
set dns-server1 2606:4700:4700::1113
set dns-server2 2606:4700:4700::1003
next
end

[Stephen_G]

Hi AntonyChen,

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.

Thanks,

[Stephen_G]

Hello AntonyChen,

We are still looking for someone to help you.

We will come back to you ASAP.

In the meantime, is this topic of any use? It may be relevant.

Regards,

[AntonyChen]

Thanks Stephen

My case is different from him

My client ipv6 work well until the pppoe reconnect and new ipv6 assigned from DHCP6 server
I found that if reduce the lease time of dhcpv6 from fortigate to a very short time about 15-30 min  config will temporatory solve this because the old ip will soon release, the problem may the windows PC does not release old ipv6 after the new one

but this is not a good solution 

[Stephen_G · Accepted solution]

Hi AntonyChen,

Sorry, but it's taken a while to find someone who can advise you. If you haven't already created a TAC support ticket, I recommend doing so.

Kind regards,

[AntonyChen]

Hi Stephen
I have aready created a TAC support but they cant help:

"I found that ISP will reset IP after a time, this is automation and doesn't cause this issue. Due to you test manually , IPv6 will not enough time for releasing.

You should find solution for DHCP lease on Client's OS.
"

[Markus_M]

Hi Antony,

it might work if you let the FortiGate be served as DHCP by the ISP, but drop DHCP there and let the FortiGate serve its own clients. That way the FortiGate knows the IPv6 addresses as you defined them and it can route them as known addresses. So basically similar to IPv4 where there is no means of DHCP from ISP to the network behind the router, but from router to network only.

Your problem, with the clients randomly coming online and receiving a 24h lease, while the routers lease is expiring 12h earlier, will cause problems if the routers IP changes and the clients are not aware of it. I guess it would work if the ISP DHCP would automatically count down the lease time based on its lease to the router and internet connection.

Best regards,

Markus