Trace recursive next-hop resolution depth, its control-plane cost and the platform recursion limit.
Recursion is a control-plane concept only: the RIB walks the chain until it reaches an interface, then writes one flattened FIB entry, so the data plane still does a single lookup. The cost appears during convergence, when every level in the chain has to be re-resolved. This is the mechanism behind BGP next-hop tracking — a BGP route recursing through an IGP route through a connected interface — and an unresolved next hop is the most common reason a route is in the BGP table but never installed.
Recursive Route
Resolution walks one RIB lookup per recursion level plus a final lookup that lands on a connected adjacency, and the result is flattened into a single FIB entry.
Reconvergence impact
Reconvergence cost ≈ levels × per-level resolution time, because each level must re-resolve in turn.
Resolution walks one RIB lookup per recursion level plus a final lookup that lands on a connected adjacency, and the result is flattened into a single FIB entry. Recursion is a control-plane concept only: the RIB walks the chain until it reaches an interface, then writes one flattened FIB entry, so the data plane still does a single lookup. The cost appears during convergence, when every level in the chain has to be re-resolved.
This is the mechanism behind BGP next-hop tracking — a BGP route recursing through an IGP route through a connected interface — and an unresolved next hop is the most common reason a route is in the BGP table but never installed.
This calculator takes 4 inputs: Recursion levels to resolve, Platform recursion limit, RIB lookup cost per level, Reconvergence cost per level. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
The next hop is probably not resolvable: it may only be covered by the default route, which most implementations refuse to recurse through for BGP. Advertise the next hop into the IGP or use a static route to it.