If the file structure is otherwise valid, extract raw packet data and re-capture with correct header:
tcpslice -w raw.pcap -d capture.pcap
(Note: tcpslice may still fail if it checks the header aggressively.)
A network engineer received a pcap from a remote site that claimed to be "Ethernet" but file command reported "pcap: DLT 276". The remote script had a bug: pcap_open_dead() was called with the wrong DLT due to an uninitialized variable. Solution: They fixed the capture script and re-ran the test. -pcap network type 276 unknown or unsupported-
Use a tool that recognizes the DLT
Convert or rewrite the capture to a supported link type If the file structure is otherwise valid, extract
Tell the analyzer to treat frames as a given link type
-E or linktype override in some builds; otherwise use editcap:
Ask vendor or check specs
Implement or load a dissector/plugin