path: root/FAQ

   The Ethereal FAQ

   Note: This is just an ASCII snapshot of the faq and may not be up to
         date. Please go to http://www.ethereal.com/faq for the up to
         date version. The version of the snapshot can be found at the
         end of this document.

   INDEX
   General Questions:

   1.1 Where can I get help?

   1.2 What protocols are currently supported?

   1.3 Are there any plans to support {your favorite protocol}?

   1.4 Can Ethereal read capture files from {your favorite network
   analyzer}?

   1.5 What devices can Ethereal use to capture packets?

   1.6 How do you pronounce Ethereal? Where did the name come from?

   Downloading Ethereal:

   2.1 I downloaded the Win32 installer, but when I try to run it, I get
   an error.

   Installing Ethereal:

   3.1 I installed an Ethereal RPM, but Ethereal doesn't seem to be
   installed; only Tethereal is installed.

   Building Ethereal:

   4.1 The configure script can't find pcap.h or bpf.h, but I have
   libpcap installed.

   4.2 Why do I get the error 

     dftest_DEPENDENCIES was already defined in condition TRUE, which
     implies condition HAVE_PLUGINS_TRUE

   when I try to build Ethereal from CVS or a CVS snapshot?

   4.3 The link failed because of an undefined reference to
   snmp_set_full_objid.

   4.4 The link fails with a number of "Output line too long." messages
   followed by linker errors. 

   4.5 The link fails on Solaris because plugin_list is undefined. 

   Using Ethereal:

   5.1 When I use Ethereal to capture packets, I see only packets to and
   from my machine, or I'm not seeing all the traffic I'm expecting to
   see from or to the machine I'm trying to monitor.

   5.2 I can't see any TCP packets other than packets to and from my
   machine, even though another sniffer on the network sees those
   packets.

   5.3 I can set a display filter just fine, but capture filters don't
   work.

   5.4 I'm entering valid capture filters, but I still get "parse error"
   errors.

   5.5 I've just installed Ethereal, and the traffic on my local LAN is
   boring.

   5.6 When I run Ethereal on Solaris 8, it dies with a Bus Error when I
   start it.

   5.7 I'm running Ethereal on Linux; why do my time stamps have only
   100ms resolution, rather than 1us resolution?

   5.8 When I try to run Ethereal on Windows, it fails to run because it
   can't find packet.dll.

   5.9 When I try to download the WinPcap driver and library, I can't get
   to the WinPcap Web site.

   5.10 I'm running Ethereal on Windows; why doesn't my my (Token Ring,
   PPP) network interface show up in the list of interfaces in the
   "Interface" item in the "Capture Preferences" dialog box popped up by
   the "Capture->Start" menu item?

   5.11 I'm running Ethereal on Windows NT/2000/XP/.NET Server; my
   machine has a PPP (dial-up POTS, ISDN, etc.) interface, and it shows
   up in the "Interface" item in the "Capture Preferences" dialog box.
   Why can no packets be sent on or received from that network while I'm
   trying to capture traffic on that interface?

   5.12 I'm running Ethereal on Windows 95/98/Me, on a machine with more
   than one network adapter of the same type; Ethereal shows all of those
   adapters with the same name, but I can't use any of those adapters
   other than the first one.

   5.13 I have an XXX network card on my machine; it doesn't show up in
   the list of interfaces in the "Interface:" field in the dialog box
   popped up by "Capture->Start", and/or Ethereal gives me an error if I
   try to capture on that interface. 

   5.14 There are no interfaces in the drop-down list of interfaces in
   the "Interface:" field in the dialog box popped up by
   "Capture->Start". 

   5.15 I have an XXX network card on my machine; if I try to capture on
   it, my machine crashes or resets itself. 

   5.16 My machine crashes or resets itself when I select "Start" from
   the "Capture" menu or select "Preferences" from the "Edit" menu. 

   5.17 Does Ethereal work on Windows ME? 

   5.18 Does Ethereal work on Windows XP? 

   5.19 Why doesn't Ethereal correctly identify RTP packets? It shows
   them only as UDP.

   5.20 Why do I get the error 

     Gdk-ERROR **: Palettized display (256-colour) mode not supported on
     Windows.
     aborting....

   when I try to run Ethereal on Windows?

   5.21 I'm capturing packets on {Windows 95, Windows 98, Windows Me};
   why are the time stamps on packets wrong? 

   5.22 When I capture on Windows in promiscuous mode, I can see packets
   other than those sent to or from my machine; however, those packets
   show up with a "Short Frame" indication, unlike packets to or from my
   machine. What should I do to arrange that I see those packets in their
   entirety? 

   5.23 How can I capture raw 802.11 packets, including non-data
   (management, beacon) packets? 

   5.24 How can I capture packets with CRC errors? 

   5.25 How can I capture entire frames, including the FCS? 

   5.26 Ethereal hangs after I stop a capture. 

   GENERAL QUESTIONS 
   Q 1.1: Where can I get help?

   A: Support is available on the ethereal-users mailing list.
   Subscription information and archives for all of Ethereal's mailing
   lists can be found at http://www.ethereal.com/lists

   Q 1.2: What protocols are currently supported?

   A: There are currently 280 supported protocols and media, listed
   below. Descriptions can be found in the ethereal(1) man page.

            802.1q Virtual LAN
            802.1x Authentication
            Address Resolution Protocol
            Ad hoc On-demand Distance Vector Routing Protocol
            Ad hoc On-demand Distance Vector Routing Protocol v6
            Aggregate Server Access Protocol
            Andrew File System (AFS)
            AOL Instant Messenger
            Apache JServ Protocol v1.3
            Appletalk Address Resolution Protocol
            AppleTalk Filing Protocol
            AppleTalk Session Protocol
            AppleTalk Transaction Protocol packet
            Async data over ISDN (V.120)
            ATM
            ATM LAN Emulation
            Authentication Header
            BACnet Virtual Link Control
            Banyan Vines
            Banyan Vines Fragmentation Protocol
            Banyan Vines SPP
            Blocks Extensible Exchange Protocol
            Boot Parameters
            Bootstrap Protocol
            Border Gateway Protocol
            Building Automation and Control Network APDU
            Building Automation and Control Network NPDU
            Cisco Auto-RP
            Cisco Discovery Protocol
            Cisco Group Management Protocol
            Cisco HDLC
            Cisco Hot Standby Router Protocol
            Cisco Interior Gateway Routing Protocol
            Cisco ISL
            Cisco SLARP
            Common Open Policy Service
            Common Unix Printing System (CUPS) Browsing Protocol
            Data
            Datagram Delivery Protocol
            Data Link SWitching
            Data Stream Interface
            DCE RPC
            DCE/RPC Conversation Manager
            DCE/RPC Endpoint Mapper
            DCE/RPC Remote Management
            DCOM OXID Resolver
            DCOM Remote Activation
            DEC Spanning Tree Protocol
            DHCPv6
            Diameter Protocol
            Distance Vector Multicast Routing Protocol
            Distributed Checksum Clearinghouse Prototocl
            Domain Name Service
            Dynamic DNS Tools Protocol
            Encapsulating Security Payload
            Enhanced Interior Gateway Routing Protocol
            Ethernet
            Extensible Authentication Protocol
            Fiber Distributed Data Interface
            File Transfer Protocol (FTP)
            Frame
            Frame Relay
            FTP Data
            GARP Multicast Registration Protocol
            GARP VLAN Registration Protocol
            General Inter-ORB Protocol
            Generic Routing Encapsulation
            Gnutella Protocol
            GPRS Tunneling Protocol
            GPRS Tunnelling Protocol v0
            GPRS Tunnelling Protocol v1
            Hummingbird NFS Daemon
            Hypertext Transfer Protocol
            ICQ Protocol
            IEEE 802.11 wireless LAN
            IEEE 802.11 wireless LAN management frame
            ILMI
            Inter-Access-Point Protocol
            Internet Cache Protocol
            Internet Content Adaptation Protocol
            Internet Control Message Protocol
            Internet Control Message Protocol v6
            Internet Group Management Protocol
            Internet Message Access Protocol
            Internet Printing Protocol
            Internet Protocol
            Internet Protocol Version 6
            Internet Relay Chat
            Internet Security Association and Key Management Protocol
            Internetwork Packet eXchange
            IP Payload Compression
            IPX Message
            IPX Routing Information Protocol
            iSCSI
            ISDN Q.921-User Adaptation Layer
            ISDN User Part
            ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol
            ISO 8073 COTP Connection-Oriented Transport Protocol
            ISO 8473 CLNP ConnectionLess Network Protocol
            ISO 8602 CLTP ConnectionLess Transport Protocol
            ISO 9542 ESIS Routeing Information Exchange Protocol
            ITU-T Recommendation H.261
            Java RMI
            Java Serialization
            Kerberos
            Kernel Lock Manager
            Label Distribution Protocol
            Layer 2 Tunneling Protocol
            Lightweight Directory Access Protocol
            Line Printer Daemon Protocol
            Link Access Procedure Balanced Ethernet (LAPBETHER)
            Link Access Procedure Balanced (LAPB)
            Link Access Procedure, Channel D (LAPD)
            Link Aggregation Control Protocol
            Link Management Protocol (LMP)
            Linux cooked-mode capture
            Local Management Interface
            LocalTalk Link Access Protocol
            Logical-Link Control
            Lucent/Ascend debug output
            Message Transfer Part Level 2
            Message Transfer Part Level 3
            Microsoft Distributed File System
            Microsoft Exchange MAPI
            Microsoft Local Security Architecture
            Microsoft Network Logon
            Microsoft Registry
            Microsoft Security Account Manager
            Microsoft Server Service
            Microsoft Spool Subsystem
            Microsoft Telephony API Service
            Microsoft Windows Browser Protocol
            Microsoft Windows Lanman Remote API Protocol
            Microsoft Windows Logon Protocol
            Microsoft Workstation Service
            MMS Message Encapsulation
            Mobile IP
            Modbus/TCP
            Mount Service
            MSNIP: Multicast Source Notification of Interest Protocol
            MS Proxy Protocol
            MTP2 Peer Adaptation Layer
            MTP 2 Transparent Proxy
            MTP 2 User Adaptation Layer
            MTP 3 User Adaptation Layer
            Multicast Router DISCovery protocol
            Multicast Source Discovery Protocol
            MultiProtocol Label Switching Header
            Name Binding Protocol
            Name Management Protocol over IPX
            NetBIOS
            NetBIOS Datagram Service
            NetBIOS Name Service
            NetBIOS over IPX
            NetBIOS Session Service
            NetWare Core Protocol
            Network Data Management Protocol
            Network File System
            Network Lock Manager Protocol
            Network News Transfer Protocol
            Network Status Monitor CallBack Protocol
            Network Status Monitor Protocol
            Network Time Protocol
            NFSACL
            NFSAUTH
            NIS+
            NIS+ Callback
            NSPI
            Null/Loopback
            OpenBSD Packet Filter log file
            Open Shortest Path First
            PC NFS
            Point-to-Point Protocol
            Point-to-Point Tunnelling Protocol
            Portmap
            Post Office Protocol
            PPP Bandwidth Allocation Control Protocol
            PPP Bandwidth Allocation Protocol
            PPP Callback Control Protocol
            PPP Challenge Handshake Authentication Protocol
            PPP Compressed Datagram
            PPP Compression Control Protocol
            PPP IP Control Protocol
            PPP Link Control Protocol
            PPP Multilink Protocol
            PPP Multiplexing
            PPPMux Control Protocol
            PPP-over-Ethernet Discovery
            PPP-over-Ethernet Session
            PPP Password Authentication Protocol
            PPP VJ Compression
            Pragmatic General Multicast
            Prism
            Protocol Independent Multicast
            Q.2931
            Q.931
            Quake III Arena Network Protocol
            Quake II Network Protocol
            Quake Network Protocol
            QuakeWorld Network Protocol
            Qualified Logical Link Control
            Radio Access Network Application Part
            Radius Protocol
            Raw packet data
            Real Time Streaming Protocol
            Real-time Transport Control Protocol
            Real-Time Transport Protocol
            Remote Procedure Call
            Remote Quota
            Remote Shell
            Remote Wall protocol
            Resource ReserVation Protocol (RSVP)
            RFC 2250 MPEG1
            RIPng
            Rlogin Protocol
            Routing Information Protocol
            Routing Table Maintenance Protocol
            RPC Browser
            RSTAT
            RX Protocol
            SADMIND
            SCSI
            Secure Socket Layer
            Sequenced Packet eXchange
            Service Advertisement Protocol
            Service Location Protocol
            Session Announcement Protocol
            Session Description Protocol
            Session Initiation Protocol
            Short Message Peer to Peer
            Signalling Connection Control Part
            Simple Mail Transfer Protocol
            Simple Network Management Protocol
            Sinec H1 Protocol
            Skinny Client Control Protocol
            SliMP3 Communication Protocol
            SMB MailSlot Protocol
            SMB Pipe Protocol
            SMB (Server Message Block Protocol)
            SNA-over-Ethernet
            SNMP Multiplex Protocol
            Socks Protocol
            Spanning Tree Protocol
            SPRAY
            SS7 SCCP-User Adaptation Layer
            SSCOP
            Stream Control Transmission Protocol
            Syslog message
            Systems Network Architecture
            TACACS
            TACACS+
            Telnet
            Time Protocol
            Time Synchronization Protocol
            Token-Ring
            Token-Ring Media Access Control
            TPKT
            Transmission Control Protocol
            Transparent Network Substrate Protocol
            Trivial File Transfer Protocol
            Universal Computer Protocol
            User Datagram Protocol
            Virtual Router Redundancy Protocol
            Virtual Trunking Protocol
            Web Cache Coordination Protocol
            Wellfleet Compression
            Who
            Wireless Session Protocol
            Wireless Transaction Protocol
            Wireless Transport Layer Security
            X11
            X.25
            X.25 over TCP
            X Display Manager Control Protocol
            Yahoo Messenger Protocol
            Yellow Pages Bind
            Yellow Pages Passwd
            Yellow Pages Service
            Yellow Pages Transfer
            Zebra Protocol

   Q 1.3: Are there any plans to support {your favorite protocol}?

   A: Support for particular protocols is added to Ethereal as a result
   of people contributing that support; no formal plans for adding
   support for particular protocols in particular future releases exist.

   Q 1.4: Can Ethereal read capture files from {your favorite network
   analyzer}?

   A: Support for particular protocols is added to Ethereal as a result
   of people contributing that support; no formal plans for adding
   support for particular protocols in particular future releases exist.

   If a network analyzer writes out files in a format already supported
   by Ethereal (e.g., in libpcap format), Ethereal may already be able to
   read them, unless the analyzer has added its own proprietary
   extensions to that format.

   If a network analyzer writes out files in its own format, or has added
   proprietary extensions to another format, in order to make Ethereal
   read captures from that network analyzer, we would either have to have
   a specification for the file format, or the extensions, sufficient to
   give us enough information to read the parts of the file relevant to
   Ethereal, or would need at least one capture file in that format AND a
   detailed textual analysis of the packets in that capture file (showing
   packet time stamps, packet lengths, and the top-level packet header)
   in order to reverse-engineer the file format.

   Note that there is no guarantee that we will be able to
   reverse-engineer a capture file format.

   Q 1.5: What devices can Ethereal use to capture packets?

   A: Ethereal can read live data from Ethernet, Token-Ring, FDDI, serial
   (PPP and SLIP) (if the OS on which it's running allows Ethereal to do
   so), 802.11 wireless LAN (if the OS on which it's running allows
   Ethereal to do so), ATM connections (if the OS on which it's running
   allows Ethereal to do so), and the "any" device supported on Linux by
   recent versions of libpcap. It can also read a variety of capture file
   formats, including:
     * libpcap/tcpdump
     * snoop
     * Shomiti
     * LanAlyzer
     * Sniffer (compressed and uncompressed)
     * MS Network Monitor
     * AIX iptrace
     * NetXray
     * Sniffer Pro
     * RADCOM
     * Lucent/Ascend debug output
     * Toshiba ISDN router "snoop" output
     * HPUX nettl
     * ISDN4BSD "i4btrace" utility.
     * Cisco Secure IDS
     * pppd log files (pppdump format)

   Q 1.6: How do you pronounce Ethereal? Where did the name come from?

   A: The English pronunciation can be found in Merriam-Webster's online
   dictionary at
   http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=ethereal.

   According to the book "Computer Networks" by Andrew Tannenbaum,
   Ethernet was named after the "luminiferous ether" which was once
   thought to carry electromagnetic radiation. Taking that into
   consideration, Ethereal seemed like an appropriate name for an
   Ethernet sniffer.

   DOWNLOADING ETHEREAL 
   Q 2.1: I downloaded the Win32 installer, but when I try to run it, I
   get an error.

   A: The program you used to download it may have downloaded it
   incorrectly. Web browsers sometimes may do this; try downloading it
   with, for example, WS_FTP from Ipswitch, or with the ftp command that
   comes with Windows - if you use the ftp command, make sure you do the
   transfer in binary mode rather than ASCII mode, by using the binary
   command before transferring the file.

   INSTALLING ETHEREAL 
   Q 3.1: I installed an Ethereal RPM, but Ethereal doesn't seem to be
   installed; only Tethereal is installed.

   A: Red Hat RPMs for Ethereal put only the non-GUI components into the
   ethereal RPM, the fact that Ethereal is a GUI program nonwithstanding;
   there's a separate ethereal-gnome RPM that includes GUI components
   such as Ethereal itself, the fact that Ethereal doesn't use GNOME
   nonwithstanding. Find the ethereal-gnome RPM, and install that also.

   BUILDING ETHEREAL 
   Q 4.1: The configure script can't find pcap.h or bpf.h, but I have
   libpcap installed.

   A: Are you sure pcap.h and bpf.h are installed? The official
   distribution of libpcap only installs the libpcap.a library file when
   "make install" is run. To install pcap.h and bpf.h, you must run "make
   install-incl". If you're running Debian or Redhat, make sure you have
   the "libpcap-dev" or "libpcap-devel" packages installed.

   It's also possible that pcap.h and bpf.h have been installed in a
   strange location. If this is the case, you may have to tweak
   aclocal.m4.

   Q 4.2: Why do I get the error 

     dftest_DEPENDENCIES was already defined in condition TRUE, which
     implies condition HAVE_PLUGINS_TRUE

   when I try to build Ethereal from CVS or a CVS snapshot?

   A: You probably have automake 1.5 installed on your machine (the
   command automake --version will report the version of automake on your
   machine). There is a bug in that version of automake that causes this
   problem; upgrade to a later version of automake (1.6 or later).

   Q 4.3: The link failed because of an undefined reference to
   snmp_set_full_objid.

   A: You probably have the shared library for UCD SNMP 4.1.1 installed
   (so that snmp_set_full_objid is a macro, rather than a routine in the
   SNMP shared library), but the `development' package for an earlier or
   later UCD SNMP library (so that snmp_set_full_objid is not defined as
   a macro, causing Ethereal to attempt to call it as a routine).

   If you are on a Linux system that uses RPMs, and the UCD SNMP packages
   are installed as RPMs, the command rpm -qa | grep snmp will report the
   versions of the SNMP packages you have installed; they should all have
   the same version number, such as 4.0.1 or 4.1.1 or 4.1.2. If they
   don't, remove the RPM for the development package (which will probably
   have a name beginning with ucd-snmp-devel) and install the version of
   the development package with the same version number as the other
   ucd-snmp packages have.

   After installing the 4.1.1 version of the UCD SNMP header files, do a
   make clean and then rebuild Ethereal.

   Q 4.4: The link fails with a number of "Output line too long."
   messages followed by linker errors. 

   A: The version of the sed command on your system is incapable of
   handling very long lines. On Solaris, for example, /usr/bin/sed has a
   line length limit too low to allow libtool to work; /usr/xpg4/bin/sed
   can handle it, as can GNU sed if you have it installed.

   On Solaris, changing your command search path to search /usr/xpg4/bin
   before /usr/bin should make the problem go away; on any platform on
   which you have this problem, installing GNU sed and changing your
   command path to search the directory in which it is installed before
   searching the directory with the version of sed that came with the OS
   should make the problem go away.

   Q 4.5: The link fails on Solaris because plugin_list is undefined. 

   A: This appears to be due to a problem with some versions of the GTK+
   and GLib packages from www.sunfreeware.org; un-install those packages,
   and try getting the 1.2.10 versions from that site, or the versions
   from The Written Word, or the versions from Sun's GNOME distribution,
   or the versions from the supplemental software CD that comes with the
   Solaris media kit, or build them from source from the GTK Web site.
   Then re-run the configuration script, and try rebuilding Ethereal. (If
   you get the 1.2.10 versions from www.sunfreeware.org, and the problem
   persists, un-install them and try installing one of the other versions
   mentioned.)

   USING ETHEREAL 
   Q 5.1: When I use Ethereal to capture packets, I see only packets to
   and from my machine, or I'm not seeing all the traffic I'm expecting
   to see from or to the machine I'm trying to monitor.

   A: This might be because the interface on which you're capturing is
   plugged into a switch; on a switched network, unicast traffic between
   two ports will not necessarily appear on other ports - only broadcast
   and multicast traffic will be sent to all ports.

   Note that even if your machine is plugged into a hub, the "hub" may be
   a switched hub, in which case you're still on a switched network.

   Note also that on the Linksys Web site, they say that their
   auto-sensing hubs "broadcast the 10Mb packets to the port that operate
   at 10Mb only and broadcast the 100Mb packets to the ports that operate
   at 100Mb only", which would indicate that if you sniff on a 10Mb port,
   you will not see traffic coming sent to a 100Mb port, and vice versa.
   This problem has also been reported for Netgear dual-speed hubs, and
   may exist for other "auto-sensing" or "dual-speed" hubs.

   Some switches have the ability to replicate all traffic on all ports
   to a single port so that you can plug your sniffer into that single
   port to sniff all traffic. You would have to check the documentation
   for the switch to see if this is possible and, if so, to see how to do
   this.

   If your machine is not plugged into a switched network, or it is and
   the port is set up to have all traffic replicated to it, the problem
   might be that the network interface on which you're capturing doesn't
   support "promiscuous" mode, or because your OS can't put the interface
   into promiscuous mode. Normally, network interfaces supply to the host
   only:
     * packets sent to one of that host's link-layer addresses;
     * broadcast packets;
     * multicast packets sent to a multicast address that the host has
       configured the interface to accept.

   Most network interfaces can also be put in "promiscuous" mode, in
   which they supply to the host all network packets they see. However,
   some network interfaces don't support promiscuous mode, and some OSes
   might not allow interfaces to be put into promiscuous mode.

   If the interface is not running in promiscuous mode, it won't see any
   traffic that isn't intended to be seen by your machine. It will see
   broadcast packets, and multicast packets sent to a multicast MAC
   address the interface is set up to receive.

   You should ask the vendor of your network interface whether it
   supports promiscuous mode. If it does, you should ask whoever supplied
   the driver for the interface (the vendor, or the supplier of the OS
   you're running on your machine) whether it supports promiscuous mode
   with that network interface.

   In the case of token ring interfaces, the drivers for some of them, on
   Windows, may require you to enable promiscuous mode in order to
   capture in promiscuous mode. Ask the vendor of the card how to do
   this.

   In the case of wireless LAN interfaces, it appears that, when those
   interfaces are promiscuously sniffing, they're running in a
   significantly different mode from the mode that they run in when
   they're just acting as network interfaces (to the extent that it would
   be a significant effor for those drivers to support for promiscuously
   sniffing and acting as regular network interfaces at the same time),
   so it may be that Windows drivers for those interfaces don't support
   promiscuous mode.

   Q 5.2: I can't see any TCP packets other than packets to and from my
   machine, even though another sniffer on the network sees those
   packets.

   A: You're probably not seeing any packets other than unicast packets
   to or from your machine, and broadcast and multicast packets; a switch
   will normally send to a port only unicast traffic sent to the MAC
   address for the interface on that port, and broadcast and multicast
   traffic - it won't send to that port unicast traffic sent to a MAC
   address for some other interface - and a network interface not in
   promiscuous mode will receive only unicast traffic sent to the MAC
   address for that interface, broadcast traffic, and multicast traffic
   sent to a multicast MAC address the interface is set up to receive.

   TCP doesn't use broadcast or multicast, so you will only see your own
   TCP traffic, but UDP services may use broadcast or multicast so you'll
   see some UDP traffic - however, this is not a problem with TCP
   traffic, it's a problem with unicast traffic, as you also won't see
   all UDP traffic between other machines.

   I.e., this is probably the same problem discussed in the previous
   question; see the response to that question.

   Q 5.3: I can set a display filter just fine, but capture filters don't
   work.

   A: Capture filters currently use a different syntax than display
   filters. Here's the corresponding section from the ethereal(1) man
   page:

   "Display filters in Ethereal are very powerful; more fields are
   filterable in Ethereal than in other protocol analyzers, and the
   syntax you can use to create your filters is richer. As Ethereal
   progresses, expect more and more protocol fields to be allowed in
   display filters.

   Packet capturing is performed with the pcap library. The capture
   filter syntax follows the rules of the pcap library. This syntax is
   different from the display filter syntax."

   The capture filter syntax used by libpcap can be found in the
   tcpdump(8) man page.

   Q 5.4: I'm entering valid capture filters, but I still get "parse
   error" errors.

   A: There is a bug in some versions of libpcap/WinPcap that cause it to
   report parse errors even for valid expressions if a previous filter
   expression was invalid and got a parse error.

   Try exiting and restarting Ethereal; if you are using a version of
   libpcap/WinPcap with this bug, this will "erase" its memory of the
   previous parse error. If the capture filter that got the "parse error"
   now works, the earlier error with that filter was probably due to this
   bug. The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions of
   libpcap have this bug, but 0.6[.x] and later versions don't.

   Versions of WinPcap prior to 2.3 are based on pre-0.6 versions of
   libpcap, and have this bug; WinPcap 2.3 is based on libpcap 0.6.2, and
   doesn't have this bug.

   If you are running Ethereal on a UNIX-flavored platform, run "ethereal
   -v", or select "About Ethereal..." from the "Help" menu in Ethereal,
   to see what version of libpcap it's using. If it's not 0.6 or later,
   you will need either to upgrade your OS to get a later version of
   libpcap, or will need to build and install a later version of libpcap
   from the tcpdump.org Web site and then recompile Ethereal from source
   with that later version of libpcap.

   If you are running Ethereal on Windows with a pre-2.3 version of
   WinPcap, you will need to un-install WinPcap and then download and
   install WinPcap 2.3.

   Q 5.5: I've just installed Ethereal, and the traffic on my local LAN
   is boring.

   A: We have a collection of strange and exotic sample capture files at
   http://www.ethereal.com/sample/

   Q 5.6: When I run Ethereal on Solaris 8, it dies with a Bus Error when
   I start it.

   A: Some versions of the GTK+ library from www.sunfreeware.org appear
   to be buggy, causing Ethereal to drop core with a Bus Error.
   Un-install those packages, and try getting the 1.2.10 version from
   that site, or the version from The Written Word, or the version from
   Sun's GNOME distribution, or the version from the supplemental
   software CD that comes with the Solaris media kit, or build it from
   source from the GTK Web site. Update the GLib library to the 1.2.10
   version, from the same source, as well. (If you get the 1.2.10
   versions from www.sunfreeware.org, and the problem persists,
   un-install them and try installing one of the other versions
   mentioned.) Similar problems may exist with older versions of GTK+ for
   earlier versions of Solaris.

   Q 5.7: I'm running Ethereal on Linux; why do my time stamps have only
   100ms resolution, rather than 1us resolution?

   A: Ethereal gets time stamps from libpcap/WinPcap, and libpcap/WinPcap
   get them from the OS kernel, so Ethereal - and any other program using
   libpcap, such as tcpdump - is at the mercy of the time stamping code
   in the OS for time stamps.

   At least on x86-based machines, Linux can get high-resolution time
   stamps on newer processors with the Time Stamp Counter (TSC) register;
   for example, Intel x86 processors, starting with the Pentium Pro, and
   including all x86 processors since then, have had a TSC, and other
   vendors probably added the TSC at some point to their families of x86
   processors.

   The Linux kernel must be configured with the CONFIG_X86_TSC option
   enabled in order to use the TSC. Make sure this option is enabled in
   your kernel.

   In addition, some Linux distributions may have bugs in their versions
   of the kernel that cause packets not to be given high-resolution time
   stamps even if the TSC is enabled. See, for example, bug 61111 for Red
   Hat Linux 7.2. If your distribution has a bug such as this, you may
   have to run a standard kernel from kernel.org in order to get
   high-resolution time stamps.

   Q 5.8: When I try to run Ethereal on Windows, it fails to run because
   it can't find packet.dll.

   A: In older versions of Ethereal, there were two binary distributions
   available for Windows, one that supported capturing packets, and one
   that didn't. The version that supported capturing packets required
   that you install the WinPcap driver; if you didn't install it, it
   would fail to run because it couldn't find packet.dll.

   The current version of Ethereal has only one binary distribution for
   Windows; that version will check whether WinPcap is installed and, if
   it's not, will disable support for packet capture.

   The WinPcap driver and libraries can be downloaded from the WinPcap
   Web site, the local mirror of the WinPcap Web site, or the
   Wiretapped.net mirror of the WinPcap site.

   Q 5.9: When I try to download the WinPcap driver and library, I can't
   get to the WinPcap Web site.

   A: As is the case with all Web sites, that site won't necessarily
   always be accessible; the server may be down due to a problem or down
   for maintenance, or there may be a networking problem between you and
   the server. You should try again later, or try the local mirror or the
   Wiretapped.net mirror.

   Q 5.10: I'm running Ethereal on Windows; why doesn't my my (Token
   Ring, PPP) network interface show up in the list of interfaces in the
   "Interface" item in the "Capture Preferences" dialog box popped up by
   the "Capture->Start" menu item?

   A: 2.02 and earlier versions of the WinPcap driver and library that
   Ethereal uses for packet capture didn't support Token Ring interfaces;
   the current version, 2.3, does support Token Ring, and the current
   version of Ethereal works with (and, in fact, requires) WinPcap 2.1 or
   later.

   If you are having problems capturing on Token Ring interfaces, and you
   have WinPcap 2.02 or an earlier version of WinPcap installed, you
   should uninstall WinPcap, download and install the current version of
   WinPcap, and then install the latest version of Ethereal.

   WinPcap doesn't support PPP WAN interfaces on Windows NT/2000/XP/.NET
   Server, so Ethereal cannot capture packets on those devices when
   running on Windows NT/2000/XP/.NET Server. Regular dial-up lines, ISDN
   lines, and various other lines such as T1/E1 lines are all PPP
   interfaces. This may cause the interface not to show up on the list of
   interfaces in the "Capture Preferences" dialog.

   For problems seen when installing the WinPcap driver or library, or
   seen when capturing, check the WinPcap FAQ, the local mirror of that
   FAQ, or the Wiretapped.net mirror of that FAQ, to see if your problem
   is mentioned there.

   Q 5.11: I'm running Ethereal on Windows NT/2000/XP/.NET Server; my
   machine has a PPP (dial-up POTS, ISDN, etc.) interface, and it shows
   up in the "Interface" item in the "Capture Preferences" dialog box.
   Why can no packets be sent on or received from that network while I'm
   trying to capture traffic on that interface?

   A: WinPcap doesn't support PPP WAN interfaces on Windows
   NT/2000/XP/.NET Server; one symptom that may be seen is that attempts
   to capture in promiscuous mode on the interface cause the interface to
   be incapable of sending or receiving packets. You can disable
   promiscuous mode using the -p command-line flag or the item in the
   "Capture Preferences" dialog box, but this may mean that outgoing
   packets, or incoming packets, won't be seen in the capture.

   Q 5.12: I'm running Ethereal on Windows 95/98/Me, on a machine with
   more than one network adapter of the same type; Ethereal shows all of
   those adapters with the same name, but I can't use any of those
   adapters other than the first one.

   A: Unfortunately, Windows 95/98/Me gives the same name to multiple
   instances of the type of same network adapter. Therefore, WinPcap
   cannot distinguish between them, so a WinPcap-based application can
   capture only on the first such interface; Ethereal is a
   libpcap/WinPcap-based application.

   Q 5.13: I have an XXX network card on my machine; it doesn't show up
   in the list of interfaces in the "Interface:" field in the dialog box
   popped up by "Capture->Start", and/or Ethereal gives me an error if I
   try to capture on that interface. 

   A: Ethereal relies on the libpcap library, and on the facilities that
   come with the OS on which it's running in order to do captures; on
   Windows, it also relies on the device driver that comes with WinPcap
   (which is a version of libpcap for Windows).

   Therefore, if the OS, the libpcap library, or the WinPcap driver don't
   support capturing on a particular network interface device, Ethereal
   won't be able to capture on that device.

   On Linux, note that you need to have "packet socket" support enabled
   in your kernel; see the "Packet socket" item in the Linux
   "Configure.help" file.

   On BSD, note that you need to have BPF support enabled in your kernel;
   see the documentation for your system for information on how to enable
   BPF support (if it's not enabled by default on your system).

   On DEC OSF/1, Digital UNIX, or Tru64 UNIX, note that you need to have
   packet filtering support in your kernel; the doconfig command will
   allow you to configure and build a new kernel with that option.

   If you are having trouble capturing on a particular network interface,
   and you've made sure that (on platforms that require it) you've
   arranged that packet capture support is present, as per the above,
   first try capturing on that device with tcpdump - or, on Windows, the
   tcpdump port to Windows, named WinDump; see the WinDump Web site, the
   local mirror of the WinDump Web site, or the Wiretapped.net mirror of
   the WinDump site, for information on using WinDump.

   If you can capture on the interface with tcpdump/WinDump, send mail to
   ethereal-users@ethereal.com giving full details of the problem,
   including
     * the operating system you're using, and the version of that
       operating system (for Linux, give both the version number of the
       kernel and the name and version number of the distribution you're
       using);
     * the type of network device you're using;
     * the error message you get from Ethereal.

   If you cannot capture on the interface with tcpdump/WinDump, this is
   almost certainly a problem with one or more of:
     * the operating system you're using;
     * the device driver for the interface you're using;
     * the libpcap/WinPcap library and, if this is Windows, the WinPcap
       device driver;

   so:
     * if you are using Windows, see the WinPcap support page (or the
       local mirror of that page) - check the "Submitting bugs" section;
     * if you are using some Linux distribution, some version of BSD, or
       some other UNIX-flavored OS, you should report the problem to the
       company or organization that produces the OS (in the case of a
       Linux distribution, report the problem to whoever produces the
       distribution).

   You may also want to ask the ethereal-users@ethereal.com and, if this
   is a UNIX-flavored platform, tcpdump-workers@tcpdump.org mailing lists
   to see if anybody happens to know about the problem and know a
   workaround or fix for the problem. In your mail, please give full
   details of the problem, as described above, and also indicate that the
   problem occurs with tcpdump/WinDump, not just with Ethereal.

   Q 5.14: There are no interfaces in the drop-down list of interfaces in
   the "Interface:" field in the dialog box popped up by
   "Capture->Start". 

   A: If you are running Ethereal on a UNIX-flavored platform, you may
   need to run Ethereal from an account with sufficient privileges to
   capture packets, such as the super-user account. Only those interfaces
   that Ethereal can open for capturing show up in that list; if you
   don't have sufficient privileges to capture on any interfaces, no
   interfaces will show up in the list.

   If you are running Ethereal on Windows NT 4.0, Windows 2000, or
   Windows XP, and this is the first time you have run a WinPcap-based
   program (such as Ethereal, or Tethereal, or WinDump, or Analyzer,
   or...) since the machine was rebooted, you need to run that program
   from an account with administrator privileges; once you have run such
   a program, you will not need administrator privileges to run any such
   programs until you reboot.

   If you are running on a UNIX-flavored platform and have sufficient
   privileges, or if you are running on Windows 95/98/Me, or if you are
   running on Windows NT 4.0/2000/XP and have administrator privileges or
   a WinPcap program has been run with those privileges since the machine
   rebooted, this is the same problem as in the previous question; see
   the answer to that question.

   Q 5.15: I have an XXX network card on my machine; if I try to capture
   on it, my machine crashes or resets itself. 

   A: This is almost certainly a problem with one or more of:
     * the operating system you're using;
     * the device driver for the interface you're using;
     * the libpcap/WinPcap library and, if this is Windows, the WinPcap
       device driver;

   so:
     * if you are using Windows, see the WinPcap support page (or the
       local mirror of that page) - check the "Submitting bugs" section;
     * if you are using some Linux distribution, some version of BSD, or
       some other UNIX-flavored OS, you should report the problem to the
       company or organization that produces the OS (in the case of a
       Linux distribution, report the problem to whoever produces the
       distribution).

   Q 5.16: My machine crashes or resets itself when I select "Start" from
   the "Capture" menu or select "Preferences" from the "Edit" menu. 

   A: Both of those operations cause Ethereal to try to build a list of
   the interfaces that it can open; it does so by getting a list of
   interfaces and trying to open them. There is probably an OS, driver,
   or, for Windows, WinPcap bug that causes the system to crash when this
   happens; see the previous question.

   Q 5.17: Does Ethereal work on Windows ME? 

   A: Yes, but if you want to capture packets, you will need to install
   the latest version of WinPcap, as 2.02 and earlier versions of WinPcap
   didn't support Windows ME. You should also install the latest version
   of Ethereal as well.

   Q 5.18: Does Ethereal work on Windows XP? 

   A: Yes, but if you want to capture packets, you will need to install
   the latest version of WinPcap, as 2.2 and earlier versions of WinPcap
   didn't support Windows XP.

   Q 5.19: Why doesn't Ethereal correctly identify RTP packets? It shows
   them only as UDP.

   A: Ethereal can identify a UDP datagram as containing a packet of a
   particular protocol running atop UDP only if
    1. The protocol in question has a particular standard port number,
       and the UDP source or destination port number is that port
    2. Packets of that protocol can be identified by looking for a
       "signature" of some type in the packet - i.e., some data that, if
       Ethereal finds it in some particular part of a packet, means that
       the packet is almost certainly a packet of that type.
    3. Some other traffic earlier in the capture indicated that, for
       example, UDP traffic between two particular addresses and ports
       will be RTP traffic.

   RTP doesn't have a standard port number, so 1) doesn't work; it
   doesn't, as far as I know, have any "signature", so 2) doesn't work.

   That leaves 3). If there's RTSP traffic that sets up an RTP session,
   then, at least in some cases, the RTSP dissector will set things up so
   that subsequent RTP traffic will be identified. Currently, that's the
   only place we do that; there may be other places.

   However, there will always be places where Ethereal is simply
   incapable of deducing that a given UDP flow is RTP; a mechanism would
   be needed to allow the user to specify that a given conversation
   should be treated as RTP. As of Ethereal 0.8.16, such a mechanism
   exists; if you select a UDP or TCP packet, the right mouse button menu
   will have a "Decode As..." menu item, which will pop up a dialog box
   letting you specify that the source port, the destination port, or
   both the source and destination ports of the packet should be
   dissected as some particular protocol.

   Q 5.20: Why do I get the error 

     Gdk-ERROR **: Palettized display (256-colour) mode not supported on
     Windows.
     aborting....

   when I try to run Ethereal on Windows?

   A: Ethereal is built using the GTK+ toolkit, which supports most
   UNIX-flavored OSes, and also supports Windows; that toolkit doesn't
   support 256-color mode on Windows - it requires HiColor (16-bit
   colors) or more. If your display supports more than 256 colors, switch
   to a display mode with more colors; if it doesn't support more than
   256 colors, you will be unable to run Ethereal.

   Q 5.21: I'm capturing packets on {Windows 95, Windows 98, Windows Me};
   why are the time stamps on packets wrong? 

   A: This is due to a bug in WinPcap. A future release of WinPcap will
   fix that bug.

   Q 5.22: When I capture on Windows in promiscuous mode, I can see
   packets other than those sent to or from my machine; however, those
   packets show up with a "Short Frame" indication, unlike packets to or
   from my machine. What should I do to arrange that I see those packets
   in their entirety? 

   A: In at least some cases, this appears to be the result of PGPnet
   running on the network interface on which you're capturing; turn it
   off on that interface.

   Q 5.23: How can I capture raw 802.11 packets, including non-data
   (management, beacon) packets? 

   A: The answer to this depends on the operating system on which you're
   running and the 802.11 interface you're using.

   Cisco Aironet cards:

   The only platforms that allow Ethereal to capture raw 802.11 packets
   on Cisco Aironet cards are:
     * Linux, with a 2.4.6 or later kernel;
     * FreeBSD 4.6 or later, as the driver in FreeBSD 4.5 has bugs that
       cause packets not to be captured correctly, and the driver in
       releases prior to 4.5 didn't support capturing raw packets.

   On FreeBSD, the ancontrol utility must be used; do not enable the full
   Aironet header via BPF, as Ethereal doesn't currently support that.

   On Linux, you will need to do

echo "Mode: rfmon" >/proc/driver/aironet/ethN/Config

   if your Aironet card is ethN. To capture traffic from any BSS, do

echo "Mode: y" >/proc/driver/aironet/ethN/Config

   and to return to the normal mode, do

echo "Mode: ess" >/proc/driver/aironet/ethN/Config

   In either case, Ethereal would have to be linked with libpcap 0.7.1 or
   later; this means that most Ethereal binary packages won't work unless
   they're statically linked with libpcap 0.7.1 or later, or they're
   dynamically linked with libpcap and your system has a libpcap 0.7.1 or
   later shared library installed (note that libpcap source package from
   tcpdump.org does not build shared libraries).

   Cards using the Prism II chip set (see this page of Linux 802.11
   information for details on wireless cards, including information on
   the chips they use):

   You can capture raw 802.11 packets with Prism II cards on Linux
   systems with the 0.1.14-pre1 or later version of the linux-wlan-ng
   drivers (see the linux-wlan page, and the linux-wlan-ng tarball
   directory), or with Solomon Peachy's patches to the linux-wlan-ng
   0.1.13 drivers (see the `0132-packet-v71.diff' link on his software
   page; the patch speaks of 0.1.13-pre2, but appears to apply to 0.1.13
   as well). If you are using the 0.1.13 drivers, you might also want his
   `0132-promisc-v23.diff' patch as well; if you are using the
   0.1.14-pre1 drivers, you might also want his
   `014p1-promiscfixes-v1.diff' patches - both of those are already in
   0.1.14-pre2.

   Those require either Solomon's patch to libpcap 0.7.1 (see his
   `libpcap-0.7.1-prism.diff' file, or his RPMs of that version of
   libpcap), or the current CVS version of libpcap, which includes his
   patch (download it from the `Current Tar files' section of the
   tcpdump.org Web site).

   You may have to run a command to put the interface into monitor mode,
   or to change other interface settings.
   Earlier versions of the linux-wlan-ng drivers don't allow Ethereal to
   directly capture raw 802.11 packets on Prism II cards; however, on
   Linux systems with the linux-wlan-ng drivers version 0.1.6, the
   Prismdump utility can be used to capture packets; it saves packets in
   a form that Ethereal can read. Prismdump can be downloaded from this
   page on the developer.axis.com Web site.

   On other platforms, capturing raw 802.11 packets on Prism II cards is
   not currently supported.

   Orinoco Silver and Gold cards:

   On Linux systems, when using either the orinoco_cs-0.09b driver or the
   driver in at least some versions of the Linux kernel, the
   `orinoco-09b-packet-1.diff' patch on the Orinoco Monitor Mode Patch
   Page should allow you to do capture raw 802.11 packets.

   The patch appears to apply to the driver in the 2.4.18 kernel, but we
   don't know whether it works; the directions on that page are for the
   pcmcia-cs drivers, not for the driver in the kernel itself.
   Note that the page indicates that not all versions of the Orinoco
   firmware support this patch. The Orinoco patches require Solomon
   Peachy's libpcap patches.

   On other platforms, capturing raw 802.11 packets on Orinoco cards is
   not currently supported.

   Other 802.11 interfaces:

   With other 802.11 interfaces, no platform allows Ethereal to capture
   raw 802.11 packets, as far as we know. If you know of other 802.11
   interfaces that are supported (note that there are many `Prism II
   cards', so your card might be a Prism II card), please let us know,
   and include URLs for sites containing any necessary patches to add
   this support.

   On platforms that don't allow Ethereal to capture raw 802.11 packets,
   the 802.11 network will appear like an Ethernet to Ethereal.

   Q 5.24: How can I capture packets with CRC errors? 

   A: Ethereal can capture only the packets that the packet capture
   library - libpcap on UNIX-flavored OSes, and the WinPcap port to
   Windows of libpcap on Windows - can capture, and libpcap/WinPcap can
   capture only the packets that the OS's raw packet capture mechanism
   (or the WinPcap driver, and the underlying OS networking code and
   network interface drivers, on Windows) will allow it to capture.

   Unless the OS can be configured to supply packets with errors such as
   invalid CRCs to the raw packet capture mechanism, Ethereal - and other
   programs that capture raw packets, such as tcpdump - cannot capture
   those packets. You will have to determine whether your OS can be so
   configured, configure it if possible, and make whatever changes to
   libpcap and the packet capture program you're using are necessary to
   support capturing those packets.

   Q 5.25: How can I capture entire frames, including the FCS? 

   A: Ethereal can't capture any data that the packet capture library -
   libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of
   libpcap on Windows - can capture, and libpcap/WinPcap can capture only
   the data that the OS's raw packet capture mechanism (or the WinPcap
   driver, and the underlying OS networking code and network interface
   drivers, on Windows) will allow it to capture.

   For any particular link-layer network type, unless the OS supplies the
   FCS of a frame as part of the frame, or can be configured to supply
   the FCS of a frame as part of the frame, Ethereal - and other programs
   that capture raw packets, such as tcpdump - cannot capture the FCS of
   a frame. You will have to determine whether your OS can be so
   configured, configure it if possible, and make whatever changes to
   libpcap and the packet capture program you're using are necessary to
   support capturing the FCS of a frame. Most if not all OSes probably do
   not support capturing the FCS of a frame on Ethernet, and probably do
   not support it on most other link-layer types.

   Q 5.26: Ethereal hangs after I stop a capture. 

   A: The most likely reason for this is that Ethereal is trying to look
   up an IP address in the capture to convert it to a name (so that, for
   example, it can display the name in the source address or destination
   address columns), and that lookup process is taking a very long time.

   Ethereal calls a routine in the OS of the machine on which it's
   running to convert of IP addresses to the corresponding names. That
   routine probably does one or more of:
     * a search of a system file listing IP addresses and names;
     * a lookup using DNS;
     * on UNIX systems, a lookup using NIS;
     * on Windows systems, a NetBIOS-over-TCP query.

   If a DNS server that's used in an address lookup is not responding,
   the lookup will fail, but will only fail after a timeout while the
   system routine waits for a reply.

   In addition, on Windows systems, if the DNS lookup of the address
   fails, either because the server isn't responding or because there are
   no records in the DNS that could be used to map the address to a name,
   a NetBIOS-over-TCP query will be made. That query involves sending a
   message to the NetBIOS-over-TCP name service on that machine, asking
   for the name and other information about the machine. If the machine
   isn't running software that responds to those queries - for example,
   many non-Windows machines wouldn't be running that software - the
   lookup will only fail after a timeout. Those timeouts can cause the
   lookup to take a long time.

   If you disable network address-to-name translation - for example, by
   turning off the `Enable network name resolution' option in the `Name
   resolution' options in the dialog box you get by selecting
   `Preferences' from the `Edit' menu - the lookups of the address won't
   be done, which may speed up the process of reading the capture file
   after the capture is stopped. You can make that setting the default by
   using the `Save' button in that dialog box; note that this will save
   all your current preference settings.

   If Ethereal hangs when reading a capture even with network name
   resolution turned off, there might, for example, be a bug in one of
   Ethereal's dissectors for a protocol causing it to loop infinitely.
   The bug should be reported to the Ethereal developers' mailing list at
   ethereal-dev@ethereal.com.

   On UNIX-flavored OSes, please try to force Ethereal to dump core, by
   sending it a SIGABRT signal (usually signal 6) with the kill command,
   and then get a stack trace if you have a debugger installed. A stack
   trace can be obtained by using your debugger (gdb in this example),
   the Ethereal binary, and the resulting core file. Here's an example of
   how to use the gdb command backtrace to do so.
        $ gdb ethereal core
        (gdb) backtrace
        ..... prints the stack trace
        (gdb) quit
        $

   The core dump file may be named "ethereal.core" rather than "core" on
   some platforms (e.g., BSD systems)

   Also, if at all possible, please send a copy of the capture file that
   caused the problem; when capturing packets, Ethereal normally writes
   captured packets to a temporary file, which will probably be in /tmp
   or /var/tmp on UNIX-flavored OSes and \TEMP on Windows, so the capture
   file will probably be there. It will have a name beginning with ether,
   with some mixture of letters and numbers after that. Please don't send
   a trace file greater than 1 MB when compressed. If the trace file
   contains sensitive information (e.g., passwords), then please do not
   send it.


   Support can be found on the ethereal-users[AT]ethereal.com mailing
   list. 
   For corrections/additions/suggestions for this page, please send email
   to: ethereal-web[AT]ethereal.com
   Last modified: Sun, August 11 2002.