pls help to achieve below quetion solution. (HCIE Carrier)

Hi sajidkhan,

Here is a guide on how to use MED:
https://support.huawei.com/enterprise/en/doc/EDOC1100028526?section=j069&topicName=example-for-configuring-the-med-attribute-to-control-route-selection

In your case you need to configure a route-policy and associate it with the bgp peer of the standby link:
[~DeviceB] route-policy 10 permit node 10
[*DeviceB-route-policy] apply cost 100
[*DeviceB-route-policy] commit
[~DeviceB-route-policy] quit
[~DeviceB] bgp 65009
[*DeviceB-bgp] peer x.x.x.x route-policy 10 export
[*DeviceB-bgp] commit

Since the link that you want to be active will advertise the default value of 0. Therefore, the BGP peer will select the route with the smaller MED value.