JN0-664: Service Provider Routing and Switching, Professional

An OSPF overload configuration makes a router appear unavailable for transit traffic while it restarts, steering transit traffic through other routers. Specifying timeout 900 automatically clears overload mode after 900 seconds; without a timeout, overload remains active until it is explicitly removed. The timeout must be configured for OSPF, native OSPFv3, and the OSPFv3 IPv4-unicast realm.

BGP multipath on R1 allows equal BGP paths learned through R2 and R3 to be retained as multiple next hops. The route for 203.0.113.128/25 must consequently show multiple next hops. A load-balancing policy must also be exported from the routing table to the forwarding table under routing-options so traffic can be distributed across those next hops.

A queue receiving traffic beyond its configured bandwidth allocation has negative bandwidth credit. By default, Junos permits that queue to use leftover bandwidth available from other queues; strict allocation must be explicitly configured to prevent this behavior.

CSNPs are transmitted periodically to synchronize link-state databases. PSNPs request missing LSPs or acknowledge received LSPs and carry LSP summary information, such as identifiers, lifetimes, sequence numbers, and checksums, rather than full LSP contents. Juniper IS-IS Overview

advertise-peer-as on R2 and R3 overrides Junos’s default suppression of routes learned from one EBGP peer when advertising them to another EBGP peer in the same AS as the originating peer. as-override on R2 and R3 replaces occurrences of the outbound peer’s AS in the AS path with the provider AS, so R1 and R4 can accept routes originating from their shared AS without triggering AS-path loop prevention.