300-410 Route Maps and Route Filtering Practice Question
This 300-410 practice question tests your understanding of route maps and route filtering. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An engineer configures Control Plane Policing (CoPP) with a policy map that includes a class-map matching BGP traffic. The policy map has a 'police' action that sets the rate-limit in bps. After applying the policy to the control plane, BGP sessions start flapping. Which is the most likely explanation?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The police rate is configured in bps, but BGP keepalives are small packets; pps should be used to avoid dropping.
CoPP rate-limits are often configured in bps by default, but for control plane traffic, pps (packets per second) is more appropriate. If the rate-limit is set in bps, it may be too low for BGP keepalive packets, which are small. The edge case is that the engineer used bps instead of pps, causing the policer to drop BGP packets.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 police rate is configured in bps, but BGP keepalives are small packets; pps should be used to avoid dropping.
Why this is correct
bps rate-limit can drop many small packets; pps is recommended for control plane traffic.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The class-map matches BGP traffic incorrectly; it should match on protocol BGP.
Why it's wrong here
Class-maps can match on protocol; the issue is rate unit.
✗
The policy map is applied to the control plane inbound, but BGP packets are sent outbound.
Why it's wrong here
BGP uses TCP, which is bidirectional; inbound policing affects received packets.
✗
The default class is not configured, causing all other traffic to be dropped.
Why it's wrong here
Default class does not affect BGP if it is matched in a specific class.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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 the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
Route Maps and Route Filtering — This question tests Route Maps and Route Filtering — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The police rate is configured in bps, but BGP keepalives are small packets; pps should be used to avoid dropping. — CoPP rate-limits are often configured in bps by default, but for control plane traffic, pps (packets per second) is more appropriate. If the rate-limit is set in bps, it may be too low for BGP keepalive packets, which are small. The edge case is that the engineer used bps instead of pps, causing the policer to drop BGP packets.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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