JN0-102 · Question #237
Which statement is true about the forwarding table?
The correct answer is B. The forwarding table is stored in the control plane and in the forwarding plane. The forwarding table is crucial for packet delivery and exists in both the control plane where it's built and the forwarding plane where it's used for high-speed lookups.
Question
Which statement is true about the forwarding table?
Options
- AThe forwarding table is stored in the control plane only.
- BThe forwarding table is stored in the control plane and in the forwarding plane.
- CThe forwarding table contains both active and inactive routes.
- DThe forwarding table can contain only a single next hop per destination.
How the community answered
(57 responses)- A4% (2)
- B86% (49)
- C2% (1)
- D9% (5)
Why each option
The forwarding table is crucial for packet delivery and exists in both the control plane where it's built and the forwarding plane where it's used for high-speed lookups.
The forwarding table is replicated to the forwarding plane, so it is not stored in the control plane only.
The Routing Engine (control plane) builds and maintains the master forwarding table, then a copy of this table is pushed to the Packet Forwarding Engine (forwarding plane). This allows the forwarding plane to perform rapid, hardware-based packet forwarding decisions without involving the control plane for every packet.
The forwarding table contains only active (best) routes; inactive routes are maintained in the routing table (RIB).
The forwarding table can contain multiple next-hops for a single destination in scenarios such as equal-cost multipath (ECMP) routing.
Concept tested: Junos forwarding table location
Source: https://www.juniper.net/documentation/us/en/software/junos/routing-basics/topics/topic-map/routing-tables-forwarding-table-overview.html
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