Quick Answer
The answer is the Egress Tunnel Router (ETR). This is correct because the ETR is the LISP device responsible for registering its own location—specifically, the IP addresses of its connected Endpoint Identifiers (EIDs)—with the mapping system, typically the Map-Server (MS), so that an Ingress Tunnel Router (ITR) can later query and find that location to forward traffic. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of the LISP control plane versus data plane roles; a common trap is confusing the ETR’s registration function with the ITR’s mapping lookup or the Map-Resolver’s (MR) query handling. Remember that the ETR “enters” the mapping into the system, while the ITR “inquires” about it. A helpful memory tip: ETR = “Enters The Registry,” and ITR = “Inquires To Resolve.”
This 350-501 practice question tests your understanding of networking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which LISP feature allows a device to register its location to a mapping system so that another device can find it?
ETR
ETR registers EID-to-RLOC mappings with the mapping system.
Map-Resolver (MR)
Why wrong: MR resolves mappings on behalf of ITRs.
Proxy ITR (PITR)
Why wrong: PITR acts as ITR for non-LISP sites.
xTR
Why wrong: xTR is a combination of ITR and ETR.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ETR
Option B is correct: In LISP, the ITR (Ingress Tunnel Router) performs mapping lookup, but the ETR (Egress Tunnel Router) registers mappings with the MR/MS (Map-Resolver/Map-Server). Option A (xTR) is both; Option C (MR) resolves mappings; Option D (PITR) is proxy ITR for non-LISP sites.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
ETR
Why this is correct
ETR registers EID-to-RLOC mappings with the mapping system.
Related concept
Read the scenario before looking for a memorised answer.
Map-Resolver (MR)
Why it's wrong here
MR resolves mappings on behalf of ITRs.
Proxy ITR (PITR)
Why it's wrong here
PITR acts as ITR for non-LISP sites.
xTR
Why it's wrong here
xTR is a combination of ITR and ETR.
Common exam traps
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 350-501 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which 350-501 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
The correct answer is: ETR — Option B is correct: In LISP, the ITR (Ingress Tunnel Router) performs mapping lookup, but the ETR (Egress Tunnel Router) registers mappings with the MR/MS (Map-Resolver/Map-Server). Option A (xTR) is both; Option C (MR) resolves mappings; Option D (PITR) is proxy ITR for non-LISP sites.
Identify which 350-501 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This 350-501 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-501 exam.
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