FireBrick FB6602, Руководство пользователя

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Network Diagnostic Tools
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DNS resolver access:-
This address is not on a local Ethernet subnet and so not allowed access.
13.2. Packet Dumping
The FireBrick includes the ability to capture packet dumps for diagnostic purposes. This might typically be used
where the behaviour of the FB6000 is not as expected, and can help identify whether other devices are correctly
implementing network protocols - if they are, then you should be able to determine whether the FB6000 is
responding appropriately. The packet dumping facility may also be of use to you to debug traffic (and thus
specific network protocols) between two hosts that the brick is routing traffic between.
This feature is provided via the FB6000's HTTP server and provides a download of a pcap format file (old
format) suitable for use with
tcpdump
or Wireshark.
A packet dump can be performed by either of these methods :-
• via the user interface, using a web-page form to setup the dump - once the capture data has been downloaded
it can be analysed using
tcpdump
or Wireshark
• using an HTTP client on another machine (typically a command-line client utility such as curl )
The output is streamed so that, when used with
curl
and
tcpdump
, you can monitor traffic in real time.
Limited filtering is provided by the FB6000, so you will normally apply any additional filtering you need via
tcpdump
.
13.2.1. Dump parameters
Table 13.1 lists the parameters you can specify to control what gets dumped. The "Parameter name" column
shows the exact parameter name to specify when constructing a URL to use with an HTTP client. The "Web-
form field" column shows the label of the equivalent field on the user interface form.
Table 13.1. Packet dump parameters
Parameter name Web-form field Function
interface Interface One or more interfaces, as
the name of the interface. e.g.
interface=WAN, also applies for
name of PPPoE on an interface
l2tp L2TP session Where L2TP is available, one
or more sessions, using the
full hex accounting ID, can
be
specified, e.g.
l2tp=002132D94AE297DFF51E01
or you can use l2tp=* followed by a
calling line ID - this sets up logging
for a session based on calling line id
when it next connects.
snaplen Snaplen The maximum capture length for a
packet can be specified, in bytes.
Default 0 (auto). See notes below.
timeout Timeout The maximum capture time can be
specified in seconds. Default 10.