The companion registration to 2042's "isis", equally undocumented.
IANA lists isis-bcast on TCP and UDP 2043, assigned to Ken Chapman, with the service name repeated as its only description and no reference document. It pairs with isis on 2042 and, like it, has nothing to do with the IS-IS routing protocol, which runs over layer 2 and uses no transport port. Nmap sees 2043 open on roughly 0.02% of hosts, so in practice this is a name in a table rather than a protocol you will meet.
Expose with care
No documented protocol means no defensible default. Identify the process behind an open 2043 before deciding anything about exposure.
$ sudo lsof -nP -iTCP:2043 -sTCP:LISTENSeen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.