Recursive and directly connected route

[luisfeliperm]

Router A and B are connected via interface giga0/1, respectively where the network is 192.168.0.0/24.
Router a g 0/1 192.168.0.1 Router B 0.2/24.

Behind Router B there is another network 10.0.0.0/24.

Then, on router A a static route is created (route 10.0.0.0 255.255.255.0 192.168.0.2).

My question is, in this scenario the route to network 10.0.0.0 is a recursive route? Considering that the next-hope is an ip that is directly connected to router A, is it still considered a recursive route?

Or a route is only recursive if the next-hop is an IP that is not directly connected, for example, a next-hop that is two hops away (very used in failover with next-hope 8.8.8.8)

The recursive route concept was confusing, as I always thought it was in a scenario where the router doesn't know the next-hop.

[ammahend]

It’s the route whose next hop is not directly connected, consider reading this post 

[luisfeliperm]

Thanks for the link to the post, analyzing it became clear to me.
From what he concludes, every route where only the next-hop IP is informed requires a second search to find an interface. Made it a recursive route, at least initially. However, there are other mechanisms such as CEF that optimize this process.

[M02@rt37]

Hello @luisfeliperm,

When Router A creates a static route for network 10.0.0.0/24 with the next-hop IP 192.168.0.2, it's not considered recursive because the next-hop IP (192.168.0.2) is directly connected to Router A through its Gig0/1 interface. In this case, Router A knows exactly how to reach the next-hop IP without any further lookups or recursion.

Recursive routes typically come into play when the next-hop IP address is not on a directly connected network, and the router needs to consult its routing table to determine how to reach that next-hop IP address.

[luisfeliperm]

This is very confusing, because even if the next hop address is directly connected, the router will have to look again in the table to find this directly connected next hop output because it needs to know which interface to exit. Example:

Table:
D 192.168.0.0 255.255.255.0 Giga 0/1
S 10.0.0.0 255.255.255.0 192.168.0.2

This way, when the destination is 10.0.0.x, the router consults the second one saying to go to 192.168.0.2, but now the router needs to find where 192.168.0.2 is, so it makes a second query to find the output that is in gig 0/1.

As a result, the router had to query twice, that is, this is a recursive route. Right?
Can we conclude that every route that has an IP as next-hop without specifying the interface is a recursive route?

[M02@rt37 · Accepted solution]

Hello @luisfeliperm,

The term "recursive route" is typically reserved for situations where the router needs to perform multiple lookups through in its routing table to determine the next-hop IP address. It's a concept more related to recursive lookups.

While the router performs a lookup to find the interface associated with 192.168.0.2, it's not referred to as a "recursive route" in standard networking terminology because the next-hop is still directly connected to the router.