Supported Platforms
Related Documentation
Understanding Indirect Next Hops
Junos OS supports the concept of an indirect next hop for all routing protocols that support indirectly connected next hops, also known as third-party next hops.
Because routing protocols such as internal BGP (IBGP) can send routing information about indirectly connected routes, Junos OS relies on routes from intra-AS routing protocols (OSPF, IS-IS, RIP, and static) to resolve the best directly connected next hop. The Routing Engine performs route resolution to determine the best directly connected next hop and installs the route to the Packet Forwarding Engine.
By default, Junos OS does not maintain the route for indirect next hop to forwarding next-hop binding on the Packet Forwarding Engine forwarding table. As a result, when a rerouting event occurs, potentially thousands of route to forwarding next-hop bindings must be updated, which increases the route convergence time. Figure 1 illustrates the route to forwarding next-hop bindings with indirect next hop disabled.
Figure 1: Route to Forwarding Next-Hop Bindings
You can enable Junos OS to maintain the indirect next hop to forwarding next-hop binding on the Packet Forwarding Engine forwarding table. As a result, fewer route to forwarding next-hop bindings need to be updated, which improves the route convergence time. Figure 2 illustrates the route to forwarding next-hop bindings with indirect next hop enabled.
Figure 2: Route to Forwarding Indirect Next-Hop Bindings
