The answer is that the CoPP police rate is too low for the volume of routing updates during redistribution, causing legitimate packets to be dropped. This occurs because the policy-map applies a 100 kbps police rate with a burst size of 15,000 bytes, which is insufficient to handle the bursty nature of routing protocol traffic—such as OSPF, EIGRP, or BGP updates—when routes are redistributed from one protocol into another. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how CoPP can inadvertently drop control plane traffic if the police rate or burst parameters are not tuned for peak loads; a common trap is to overlook the exceeded packet count in the show policy-map output, which directly indicates the root cause. Remember the memory tip: “If CoPP drops routing updates, check the burst—small bc/be values choke redistribution.”
300-410 Route Redistribution Practice Question
This 300-410 practice question tests your understanding of route redistribution. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer configures CoPP to protect the control plane, but after redistributing routes, some legitimate routing updates are dropped. Router R1 config:
control-plane
service-policy input COPP
!
class-map match-all ROUTING
match access-group name ROUTING
!
policy-map COPP
class ROUTING
police 100000 15000 15000 conform-action transmit exceed-action drop
!
access-list ROUTING permit tcp any any eq bgp
access-list ROUTING permit udp any any eq 520
access-list ROUTING permit ospf any any
R1# show policy-map control-plane input
Class-map: ROUTING (match-all)
100 packets, 10000 bytes
5 minute offered rate 0 bps
drop rate 0 bps
Match: access-group name ROUTING
police:
cir 100000 bps, bc 15000 bytes, be 15000 bytes
conformed 90 packets, 9000 bytes; actions: transmit
exceeded 10 packets, 1000 bytes; actions: drop
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The CoPP police rate is too low for the volume of routing updates during redistribution, causing drops.
The CoPP policy is policing routing protocol traffic at 100 kbps, which may be insufficient during redistribution bursts. The exceeded drops indicate that some packets are being dropped, likely due to the burst size being too small. The fix is to increase the police rate or burst size to accommodate the redistribution traffic.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The CoPP police rate is too low for the volume of routing updates during redistribution, causing drops.
Why this is correct
Redistribution generates many routing updates; the police rate is insufficient, leading to drops.
The access-list is missing EIGRP protocol, causing EIGRP packets to be dropped.
Why it's wrong here
The ACL includes OSPF but not EIGRP; however, the drops are on matched traffic, not unmatched.
✗
The class-map is match-all, which requires all conditions to match, but only one ACL is present.
Why it's wrong here
Match-all with one ACL is fine; it matches that ACL.
✗
The policy-map is applied to the input of the control-plane, but redistribution uses output.
Why it's wrong here
CoPP applies to incoming control-plane traffic, which includes routing updates.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
Route Redistribution — This question tests Route Redistribution — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The CoPP police rate is too low for the volume of routing updates during redistribution, causing drops. — The CoPP policy is policing routing protocol traffic at 100 kbps, which may be insufficient during redistribution bursts. The exceeded drops indicate that some packets are being dropped, likely due to the burst size being too small. The fix is to increase the police rate or burst size to accommodate the redistribution traffic.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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