A community-college host cannot reach a shared service in another VN even though underlay ping between locators works. Which overlay troubleshooting focus is most appropriate?
Select an answer to reveal the explanation.
Short Explanation
If the roads between switches are fine but the destination still looks unknown, your phone book entry is probably missing. That phone book is LISP map-cache / map resolution for the EID. Underlay ping only proves locator reachability—it does not guarantee the overlay knows where the shared service lives.
Full Explanation
When a community-college host cannot reach a shared service in another VN while underlay pings between locators work, focus overlay troubleshooting on LISP map-cache / map-resolution state for the destination EID. Overlay reachability can fail independently of underlay locator ping when mappings, policy, or VN fusion are wrong.
Immediately replacing the underlay IGP with static routes between all access VLANs attacks the wrong plane and damages underlay design.
Disabling VXLAN campus-wide and bridging the two VNs at Layer 2 on the core abandons fabric segmentation to paper over a mapping/policy issue.
Clearing all AAA sessions globally before checking any fabric mapping tables is disruptive and may be unrelated to EID resolution.
Exam caveat: also verify whether the destination is supposed to be reachable across VNs via shared services—map-cache misses and intentional policy denies look similar until you check design intent.
Operational check: on the source edge, inspect LISP map-cache for the destination EID/RLOC, compare with CP map-server registrations, and test after correcting mapping or fusion. Capture findings in the college overlay troubleshooting playbook. In municipal operations, record the rationale in the change ticket so future on-call staff know which control was chosen and which failure modes the rejected options would create for city services. Re-validate after the next maintenance window that the same control still holds under the platform code and policy revisions used by the civic network team.