i was recently bitten by a cousin of this
research router getting an ebgp multi-hop full feed from 147.28.0.1 (address is relevant)
it is on a lan with a default gateway 42.666.77.11 (address not relevant), so it has
ip route 0.0.0.0 0.0.0.0 42.666.77.11
massive flapping results.
it seems it gets the bgp route for 147.28.0.0/16 and then can not resolve the next hop. it would not recurse to the default exit.
of course it was solved by
ip route 147.28.0.0 255.255.0.0 42.666.77.11
but i do not really understand in my heart why i needed to do this.
last time severall years ago on cisco I used a route-map to rewrite the next-hop. route-map xx-in permit 10 set ip next-hop 42.666.77.11 route-map xx-out permit 10 set ip next-hop x.x.x.x neighbor 147.28.0.1 remote-as yyy neighbor 147.28.0.1 ebgp-multihop 8 neighbor 147.28.0.1 route-map xx-in in neighbor 147.28.0.1 route-map xx-out out something like this.