A multihomed Ethernet Segment shows an unexpected Designated Forwarder on city leaf peers. What should troubleshooting examine first at professional depth?
Select an answer to reveal the explanation.
Short Explanation
Weird DF? Check the ESI wiring and election settings on that multihomed segment — that is who wins the forwarding badge. Underlay IGP choice is not the DF referee, and deleting Type-2s or killing EVPN is not troubleshooting.
Full Explanation
Unexpected Designated Forwarder results on a multihomed Ethernet Segment should drive troubleshooting to ESI configuration consistency and DF election parameters/outcomes on that segment first. Peers must share the same ESI value and agree on DF election; otherwise the municipal segment can blackhole or duplicate BUM. Whether the underlay uses IS-IS instead of EBGP does not alone elect the DF. Deleting all Type-2 routes so DF falls back to STP root priority is wrong. Disabling EVPN on one peer permanently so the other always forwards without ESI is a brute-force outage, not professional ESI troubleshooting. Exam caveat: DF can look wrong after timed failover tests if operators expect sticky behavior—verify algorithm results against configured preferences and timers rather than against tribal memory. Operational check: compare ESI values, DF election state, and interface multihoming mode on both city leaves; generate BUM; confirm a single DF; reconcile any mismatch and retest failover. Export DF election state to the municipal monitoring stack for every dual-homed Ethernet Segment marked production-critical. Export DF election state to the municipal monitoring stack for every dual-homed Ethernet Segment marked production-critical.