when to use this command " neighbor [A.B.C.D] ebgp-multihop "

[krahulbgp]

when to use this command " neighbor [A.B.C.D] ebgp-multihop "

[balaji.bandi]

check below example easy to understand :

https://networklessons.com/bgp/ebgp-multihop

[MHM Cisco World]

the eBGP use TTL =1 
if eBGP neighbor is far than one hop then TTL will be Zero and BGP Update will drop 
here we use eBGP-multihop to increase TTL to be 255 or any other value you want.