Hello @FrankHu114051 ,
one of the most interesting features of IOS XR is the per member link BFD on BE bundle
see
https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k-r7-1/routing/configuration/guide/b-routing-cg-asr9000-71x/b-routing-cg-asr9000-71x_chapter_0100.html#ID670
This is the recommended way to configure BFD on a BE bundle, because actually there is a BFD session over each member link allowing for faster detection of a member link failure of the bundle-ethernet.
" The BFD agent on each bundle member link monitors state changes on the link. BFD agents for sessions running on bundle member links communicate with a bundle manager. The bundle manager determines the state of member links and the overall availability of the bundle. The state of the member links contributes to the overall state of the bundle based on the threshold of minimum active links or minimum active bandwidth that is configured for that bundle. "
>> If the BE interface is flapping somehow and I don't want ISIS flaps
if the whole BE interface is flapping this means that the bundle is not stable
A possible can be the support of dampening over the BFD session
>> The dampening command was added to minimize BFD session flapping and delay session startup.
However, when using BFD the basic idea is to make the routing protocols IS-IS or also others as much as reactive as possible without increasing the use of main CPU on the route processor.
So this second request is in some way the opposite.
note: with per member link BFD you will get a BFD session over each member link but IS-IS hellos are sent only 1 per direction and over an active link using non IP load balancing scheme.
Hope to help
Giuseppe
