400-007 · Question #203
What is a description of a control plane action?
The correct answer is D. hosts locating routers that reside on attached links using the IPv6 Neighbor Discover Protocol. The control plane builds and maintains topology and reachability information, while the data plane performs the actual per-packet forwarding based on tables the control plane creates.
Question
What is a description of a control plane action?
Options
- Ade-encapsulating and re-encapsulating a packet in a data-link frame
- Bmatching the destination MAC address of an Ethernet frame to the MAC address table
- Cmatching the destination IP address of an IP packet to the IP routing table
- Dhosts locating routers that reside on attached links using the IPv6 Neighbor Discover Protocol
How the community answered
(69 responses)- A1% (1)
- B1% (1)
- C4% (3)
- D93% (64)
Why each option
The control plane builds and maintains topology and reachability information, while the data plane performs the actual per-packet forwarding based on tables the control plane creates.
De-encapsulating and re-encapsulating a packet in a data-link frame is a data plane action performed by routers at each hop as they forward packets between different Layer 2 segments.
Matching a destination MAC address against the MAC address table to make a Layer 2 forwarding decision is a data plane action performed by switches on a per-frame basis.
Matching a destination IP address against the IP routing table to determine the next hop and forward a packet is a data plane action - the routing table is built by the control plane, but the lookup and forwarding operation itself is data plane.
IPv6 NDP Router Solicitation and Advertisement messages are a control plane function because hosts use them to discover routers on attached links and build reachability information - this process populates forwarding state rather than performing forwarding itself.
Concept tested: Control plane versus data plane function identification
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_basic/configuration/xe-16/ip6b-xe-16-book/ip6-neigh-disc.html
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