@ARGamingPK1 

Hi, Nice to see you again.

It is suggested to have a look at this post, and some users might explain better than I did:

https://www.reddit.com/r/ipv6/comments/18z4xw8/how_ipv6_prefix_delegation_decides_its_prefix/

Deco doesn't support DHCPv6-PD. If there is another router behind Deco, for example:

ISP modem----Deco router#1---HG8245H router#2

ISP will issue a WAN IP (from the provider's network) and a dedicated whole prefix delegated to Deco. As Deco doesn't support DHCPv6-PD, there will be no prefix delegation for HG8245H. In this way, usually one of the routers needs to set IPV6 into "Bridge mode" to permit the advertisements to pass through to the clients behind it.

For your network topology:

ISP modem----HG8245H router#2---Deco router#1

I think HG8245H doesn't support  DHCPv6-PD either, and it can't re-advertise the prefix to Deco.

So, do you not want to use "Bridge Mode" on Deco IPV6 configuration?

Or "Bridge Mode" used to provide IPV6 addresses for Deco connected clients, but now it no longer works?

(PS: IPV6 is one of the advanced features for the NAT router. When Deco is in AP mode, its NAT function has been disabled, so it doesn't have IPV6 anymore in AP mode.)

Thank you very much.

Best regards.

  @David-TP So what can i do now? Any solution?

  @ARGamingPK1 

Hi, you haven't let me know which one is your main issue.

So, do you not want to use "Bridge Mode" on Deco IPV6 configuration?

----If you don't want to use Bridge Mode on Deco, you might consider setting Pass-through/Bridge mode on the Huawei gateway.

Or "Bridge Mode" used to provide IPV6 addresses for Deco connected clients, but now it no longer works?

The root cause is still not clear under this situation. If you unplug Deco M4, then connect a laptop directly to the Huawei gateway. Will the PC get a valid IPV6 address?

Best regards.

  @David-TP This is my IPV6 address on phone so sometimes IPV6 address got disappeared from all of my devices and to get back IPV6 address i have to restart my Deco system after every few minutes or hours in Router Mode to get IPV6 address on Bridge Mode in IPV6

  @ARGamingPK1 

Hi, can you consistently reproduce this issue? or how often did you usually run into this issue?

 When Deco is in Bridge Mode, both Deco and its connected devices will receive IPV6 addresses from the Huawei router.  I tend to think there might be something wrong with the Huawei router. Before restarting Deco to get back the IPV6 addresses, if these devices connect to Huawei WiFi, will they receive the IPV6 addresses and have an internet connection?

As for the attached picture on the mobile phone, there is a valid IPV6 address. But the IPV6 internet connection test seems failed(neither did IPV4)

Did you save it when the phone was getting IPv6 addresses properly, but has no IPV6 internet access?

(By the way, may I know the analysis tools/Apps you used here to check the network information?)

Best regards.

  @David-TP Currently i'm using Deco M4 into AP Mode and all of my devices getting IPV6 from Huawei router but in Router Mode when i turn ON (IPV6) on Bridge Mode so the devices get internet connection for few minutes or hours from IPV6 but then IPV6 address disappeared from my phone, tablet and i checked on my sister phone too. But working fine on AP Mode (IPV6) keeps connected and not gonna be disappeared but i don't want to use AP Mode because my ISP router could'nt handle 25/30 devices at a time.