D-Link DFL-260 Product Manual - Page 71

Note: NetDefendOS keeps track of saved files, Filter Expressions, Downloading the Output File

Page 71 highlights

2.6. The pcapdump Command Chapter 2. Management and Maintenance It is possible to have multiple pcapdump executions being performed at the same time. The following points describe this feature: 1. All capture from all executions goes to the same memory buffer. The command can be launched multiple times with different interfaces specified. In this case the packet flow for the different executions will be grouped together in different sections of the report. If a clearer picture of packets flowing between interfaces is required in the output then it is best to issue one pcapdump command with the interfaces of interest specified. 2. If no interface is specified then the capture is done on all interfaces. 3. The -stop option without an interface specified will halt capture on all interfaces. 4. pcapdump prevents capture running more than once on the same interface by detecting command duplication. Filter Expressions Seeing all packets passing through a particular interface often provides an excess of information to be useful. To focus on particular types of traffic the pcapdump command has the option to add an filter expression which has one of the following forms: -eth= - Filter on source or destination MAC address. -ethsrc= - Filter on source MAC address. -ethdest= - Filter on destination MAC address. -ip= - Filter source or destination IP address. -ipsrc= - Filter on source IP address. -ipdest= - Filter on destination IP address. -port= - Filter on source or destination port number. -srcport= - Filter on source port number. -destport= - Filter on destination port number. -proto= - Filter on protocol where id is the decimal protocol id. - - Instead of the protocol number, the protocol name alone can be specified and can be one of -tcp, -udp or -icmp. Downloading the Output File As shown in one of the examples above, the -write option of pcapdump can save buffered packet information to a file on the NetDefend Firewall. These output files are placed into the NetDefendOS root directory and the file name is specified in the pcapdump command line, usually with a filetype of .cap. The name of output files must follow certain rules which are described below. Files can then be downloaded to the local workstation using Secure Copy (SCP) (see Section 2.1.6, "Secure Copy"). A list of all files in the NetDefendOS root directory can be viewed by issuing the ls CLI command. The -cleanup option will erase any saved pcapdump files (including any left over from earlier uses of the command) so cleanup should only be done after file download is complete. Note: NetDefendOS keeps track of saved files NetDefendOS keeps track of all files created by pcapdump. This is true even between system restarts so the -cleanup option is always able to delete all files from the firewall's memory. Output File Naming Restrictions 71

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It is possible to have multiple
pcapdump
executions being performed at the same time. The
following points describe this feature:
1.
All capture from all executions goes to the same memory buffer.
The command can be launched multiple times with different interfaces specified. In this case
the packet flow for the different executions will be grouped together in different sections of the
report.
If a clearer picture of packets flowing between interfaces is required in the output then it is best
to issue one
pcapdump
command with the interfaces of interest specified.
2.
If no interface is specified then the capture is done on all interfaces.
3.
The
-stop
option without an interface specified will halt capture on all interfaces.
4.
pcapdump
prevents capture running more than once on the same interface by detecting
command duplication.
Filter Expressions
Seeing all packets passing through a particular interface often provides an excess of information to
be useful. To focus on particular types of traffic the
pcapdump
command has the option to add an
filter expression
which has one of the following forms:
-eth=<macaddr>
- Filter on source or destination MAC address.
-ethsrc=<macaddr>
- Filter on source MAC address.
-ethdest=<macaddr>
- Filter on destination MAC address.
-ip=<ipaddr>
- Filter source or destination IP address.
-ipsrc=<ipaddr>
- Filter on source IP address.
-ipdest=<ipaddr>
- Filter on destination IP address.
-port=<portnum>
- Filter on source or destination port number.
-srcport=<portnum>
- Filter on source port number.
-destport=<portnum>
- Filter on destination port number.
-proto=<id>
- Filter on protocol where id is the decimal protocol id.
-<protocolname>
- Instead of the protocol number, the protocol name alone can be specified and
can be one of
-tcp
,
-udp
or
-icmp
.
Downloading the Output File
As shown in one of the examples above, the
-write
option of
pcapdump
can save buffered packet
information to a file on the NetDefend Firewall.
These output files are placed into the NetDefendOS root directory and the file name is specified in
the
pcapdump
command line, usually with a filetype of
.cap
. The name of output files must follow
certain rules which are described below. Files can then be downloaded to the local workstation using
Secure Copy (SCP) (see
Section 2.1.6, “Secure Copy”
). A list of all files in the NetDefendOS root
directory can be viewed by issuing the
ls
CLI command.
The
-cleanup
option will erase any saved
pcapdump
files (including any left over from earlier uses
of the command) so cleanup should only be done after file download is complete.
Note: NetDefendOS keeps track of saved files
NetDefendOS keeps track of all files created by
pcapdump
. This is true even between
system restarts so the
-cleanup
option is always able to delete all files from the
firewall's memory.
Output File Naming Restrictions
2.6. The pcapdump Command
Chapter 2. Management and Maintenance
71