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MERGECAP(1)		 The Ethereal Network Analyzer		   MERGECAP(1)

       mergecap - Merges two capture files into one

       mergecap [ -hva ] [ -s snaplen ] [ -F file format ]
       [ -T encapsulation type ] -w outfile infile ...

       Mergecap is a program that combines multiple saved capture files into a
       single output file specified by the -w argument.	 Mergecap knows how to
       read libpcap capture files, including those of tcpdump, Ethereal, and
       other tools that write captures in that format.	In addition, Mergecap
       can read capture files from snoop and atmsnoop, Shomiti/Finisar
       Surveyor, Novell LANalyzer, Network General/Network Associates
       DOS-based Sniffer (compressed or uncompressed), Microsoft Network
       Monitor, AIX's iptrace, Cinco Networks NetXRay, Network Associates
       Windows-based Sniffer, AG Group/WildPackets
       EtherPeek/TokenPeek/AiroPeek, RADCOM's WAN/LAN analyzer, Lucent/Ascend
       router debug output, HP-UX's nettl, the dump output from Toshiba's ISDN
       routers, the output from i4btrace from the ISDN4BSD project, the output
       in IPLog format from the Cisco Secure Intrusion Detection System, pppd
       logs (pppdump format), the output from VMS's TCPIPtrace utility, the
       text output from the DBS Etherwatch VMS utility, and traffic capture
       files from Visual Networks' Visual UpTime.  There is no need to tell
       Mergecap what type of file you are reading; it will determine the file
       type by itself.	Mergecap is also capable of reading any of these file
       formats if they are compressed using gzip.  Mergecap recognizes this
       directly from the file; the '.gz' extension is not required for this

       By default, it writes the capture file in libpcap format, and writes
       all of the packets in both input capture files to the output file.  The
       -F flag can be used to specify the format in which to write the capture
       file; it can write the file in libpcap format (standard libpcap format,
       a modified format used by some patched versions of libpcap, the format
       used by Red Hat Linux 6.1, or the format used by SuSE Linux 6.3), snoop
       format, uncompressed Sniffer format, Microsoft Network Monitor 1.x
       format, the format used by Windows-based versions of the Sniffer
       software, and the format used by Visual Networks' software.

       Packets from the input files are merged in chronological order based on
       each frame's timestamp, unless the -a flag is specified.	 Mergecap
       assumes that frames within a single capture file are already stored in
       chronological order.  When the -a flag is specified, packets are copied
       directly from each input file to the output file, independent of each
       frame's timestamp.

       If the -s flag is used to specify a snapshot length, frames in the
       input file with more captured data than the specified snapshot length
       will have only the amount of data specified by the snapshot length
       written to the output file.  This may be useful if the program that is
       to read the output file cannot handle packets larger than a certain
       size (for example, the versions of snoop in Solaris 2.5.1 and Solaris
       2.6 appear to reject Ethernet frames larger than the standard Ethernet
       MTU, making them incapable of handling gigabit Ethernet captures if
       jumbo frames were used).

       The output file frame encapsulation type is set to the type of the
       input files, if all input files have the same type.  If not all of the
       input files have the same frame encapsulation type, the output file
       type is set to WTAP_ENCAP_PER_PACKET.  Note that some capture file
       formats, most notably libpcap, do not currently support
       WTAP_ENCAP_PER_PACKET.  This combination will cause the output file
       creation to fail.

       If the -T flag is used to specify a frame encapsulation type, the
       encapsulation type of the output capture file will be forced to the
       specified type, rather than being the type appropriate to the
       encapsulation type of the input capture files.  Note that this merely
       forces the encapsulation type of the output file to be the specified
       type; the packet headers of the packets will not be translated from the
       encapsulation type of the input capture file to the specified
       encapsulation type (for example, it will not translate an Ethernet
       capture to an FDDI capture if an Ethernet capture is read and '-T fddi'
       is specified).

       -w  Sets the output filename.

       -F  Sets the file format of the output capture file.

       -T  Sets the packet encapsulation type of the output capture file.

       -a  Causes the frame timestamps to be ignored, writing all packets from
	   the first input file followed by all packets from the second input
	   file.  By default, when -a is not specified, the contents of the
	   input files are merged in chronological order based on each frame's
	   timestamp.  Note: when merging, mergecap assumes that packets
	   within a capture file are already in chronological order.

       -v  Causes mergecap to print a number of messages while it's working.

       -s  Sets the snapshot length to use when writing the data.

       -h  Prints the version and options and exits.

       tcpdump(8), pcap(3), ethereal(1), editcap(1)

       Mergecap is based heavily upon editcap by Richard Sharpe
       <> and Guy Harris <>.

       Mergecap is part of the Ethereal distribution.  The latest version of
       Ethereal can be found at

	 Original Author
	 -------- ------
	 Scott Renfro		  <>


3rd Berkeley Distribution	     0.9.3			   MERGECAP(1)

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