The correct answer is to increase the BGP hold time on PE1 to 180 seconds. This resolves the issue because the low-end CE router’s overloaded CPU cannot reliably send BGP keepalives within the default 90-second hold timer, causing the session to drop with a “Hold Timer Expired” error. By adjusting the hold timer to 180 seconds, you give the slow peer more time to respond, which directly addresses the root cause without altering the IGP or LDP configuration. On the Cisco SPCOR 350-501 exam, this scenario tests your understanding of BGP timer tuning for slow peers—a common trap is to mistakenly adjust OSPF timers or suppress routes, but the key is recognizing that BGP keepalive failures stem from CPU constraints, not network congestion. Remember the memory tip: “Hold the line for slow peers—double the default to keep them alive.”
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. 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.
You are a network engineer at a service provider. Your network uses MPLS L3VPN with OSPF as the IGP and LDP for label distribution. A customer has two sites connected to different PEs (PE1 and PE2) in the same VPN. The customer's CE routers are running eBGP with the PEs. Recently, the customer reports that traffic between the two sites is intermittently dropping. Upon investigation, you find that the BGP session between PE1 and the CE at site A goes down briefly every few minutes. The logs on PE1 show BGP notifications with error code 'Hold Timer Expired'. The CE router at site A is a low-end device with limited CPU. What is the most likely cause and the best course of action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
✓
Increase the BGP hold time on PE1 to 180 seconds.
The BGP session drops due to 'Hold Timer Expired' because the low-end CE router's CPU is overloaded, causing it to fail sending BGP keepalives within the default 90-second hold time. Increasing the hold time on PE1 to 180 seconds (option D) gives the CE more time to send keepalives, reducing false timeouts. This directly addresses the root cause—insufficient CPU to maintain timely keepalives—without changing routing protocols or suppressing routes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Configure BGP route dampening on PE1 to suppress flapping routes.
Why it's wrong here
Route dampening punishes flapping routes but does not fix the root cause of the BGP session dropping.
✗
Disable LDP on the link between PE1 and CE1.
Why it's wrong here
LDP is used for label distribution in the core, not between PE and CE, and is unrelated to BGP keepalives.
✗
Change the IGP from OSPF to IS-IS to reduce routing updates.
Why it's wrong here
The IGP does not affect BGP keepalive timing; the issue is BGP session stability.
✓
Increase the BGP hold time on PE1 to 180 seconds.
Why this is correct
Increasing the hold time gives the CE more time to send keepalives, reducing session drops.
Clue confirmation
The clue words "best", "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that route dampening or IGP changes fix BGP session stability issues, when the real problem is a mismatch in BGP timers due to peer resource constraints.
Detailed technical explanation
How to think about this question
BGP hold time is negotiated during session establishment to the lower of the two peers' configured values; the default is 90 seconds (RFC 4271). On low-end CEs, CPU starvation can delay keepalive transmission beyond this window, causing the PE to declare the session dead. Increasing the hold time to 180 seconds (or adjusting keepalive interval to 1/3 of hold time) provides a larger tolerance for transient CPU spikes, a common mitigation in service provider networks with resource-constrained CPE.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the BGP hold time on PE1 to 180 seconds. — The BGP session drops due to 'Hold Timer Expired' because the low-end CE router's CPU is overloaded, causing it to fail sending BGP keepalives within the default 90-second hold time. Increasing the hold time on PE1 to 180 seconds (option D) gives the CE more time to send keepalives, reducing false timeouts. This directly addresses the root cause—insufficient CPU to maintain timely keepalives—without changing routing protocols or suppressing routes.
What should I do if I get this 350-501 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best", "most likely". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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