@Capmkwifi Deco M4R has 1000 Mbps ports. You can check again after using CAT6 ethernet cable.

  @Capmkwifi 

Hi,
You can try the following steps to see if the speed improves.
  1. Open the Deco app, go to More > ECO Mode, and ensure that ECO Mode is disabled.
  2. Go to More > QoS, and ensure QoS is disabled. If you don't see an on/off switch for QoS, set it back to standard and remove all priority devices.
  3. Go to More > Advanced > NAT Forwarding, and disable SIP ALG and UPnP.

If the same phenomenon persists, please confirm the following information.
  1. How many Deco nodes do you have? Are they Deco M4? Please describe your network diagram in detail.
  2. What's the LED status on your Deco nodes? 
  3. Are your Deco nodes displaying the offline status in the Deco app so you can't manage them?

Best Regards

  @Solla-topee My Deco M4 ethernet port also changed from 1000 Mbps to 100 Mbps after electricity came back. Everytime when electricity came back ethernet port speed changed from 1000 Mbps to 100 Mbps and i have to reboot Deco system everytime. Here is a screenshot below of my ONT. My Deco is connected on Port 1.

  @ARGamingPK1 

Hi, 
The two Ethernet ports on the Deco M4 are Gigabit ports. The Ethernet link speed is not only related to the Deco, but also the modem's port and the Ethernet cable.
If the link speed on your modem's page is 100 Mbps, please confirm whether the Ethernet ports on your modem are 1000 Mbps. You can try changing the modem or Deco ports and using a different Ethernet cable to see if the Ethernet link speed improves. 
Best Regards

  @Solla-topee I'm using CAT6 cable since 4-5 years and now suddenly speed changed from 1000 Mbps to 100 Mbps on Deco M4. Do i need to change cable or do i need to change ethernet clips?

  @ARGamingPK1 

Hi, 
If you have a different Ethernet cable, feel free to try to change the cable between the main Deco and the Huawei ONT.

What do you mean by "ethernet clips"?
Best Regards

  @Solla-topee I mean RJ45 Connectors.