Mausezahn User's Guide

Part One - Direct Mode

Author: Herbert Haas
herbert AT perihel DOT at
Revision: 0.38.1
Date: 2010-02-10
Copyright: Copyright (c) 2007-2009 by Herbert Haas.


1   Note

This User's Guide explains Mausezahn's direct mode which allows you to create frames and packets right from the Linux command line. This mode is the legacy mode; it is NOT multi-threaded and lacks Mausezahn's advanced features which are integrated in the newer interactive mode.

2   What is Mausezahn?

Mausezahn is a fast traffic generator written in C which allows you to send nearly every possible and impossible packet. Mausezahn can be used for example

  • As traffic generator (e. g. to stress multicast networks)
  • For penetration testing of firewalls and IDS
  • For DoS attacks on networks (for audit purposes of course)
  • To find bugs in network software or appliances
  • For reconnaissance attacks using ping sweeps and port scans
  • To test network behaviour under strange circumstances (stress test, malformed packets, ...)
  • As didactical tool during lab exercises

...and more. Mausezahn is basically a versatile packet creation tool on the command line with a simple syntax and online help. It could also be used within (bash-) scripts to perform combination of tests.

Currently Mausezahn is only available for Linux (and other UNIX-like) platforms. There will be no Windows version.

3   Disclaimer and License

Mausezahn is basically a traffic generator as well as a network and firewall testing tool. Don't use this tool when you are not aware of its consequences or have only little knowledge about networks and data communication. If you abuse Mausezahn for unallowed attacks and get caught, or damage something of your own, then this is completely your fault.

Since version 0.33 Mausezahn is licensed under GPLv2

4   Basics

4.1   How to specify hex digits

Many arguments allow direct byte input. Bytes are represented as two hexadecimal digits. Multiple bytes must be separated either by spaces, colons, or dashes -- whatever you prefer. The following byte strings are equivalent:

"aa:bb cc-dd-ee ff 01 02 03-04 05"

"aa bb cc dd ee ff:01:02:03:04 05"

As first example, you may want to send an arbitrary fancy (possibly invalid) frame right through your network card:

# mz ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:08:00:ca:fe:ba:be

or equivalently but more readable:

# mz ff:ff:ff:ff:ff:ff-ff:ff:ff:ff:ff:ff-08:00-ca:fe:ba:be

4.2   Basic operations

All major command line options are listed when you execute Mausezahn without arguments.

For practical usage keep the following special (not so widely known) options in mind:

-r                    Multiplies the specified delay with a random value.
-p <length>           Pad the raw frame to specified length (using random

-P <ASCII Payload>    Use the specified ASCII payload.
-f <filename>         Read the ASCII payload from a file.
-F <filename>         Read the hexadecimal payload from a file.

-S                    Simulation mode: DOES NOT put anything on the wire.
                      This is typically combined with one of the verbose
                      modes (-v or V).

Many options require a keyword or a number but the -t option is an exception since it requires both a packet type (such as ip, udp, dns, etc) and an argument string which is specific for that packet type.

Here are some simple examples:

# mz -t help
# mz -t tcp help
# mz eth3 -t udp sp=69,dp=69,p=ca:fe:ba:be

Note: Don't forget that on the CLI the Linux shell (usually the Bash) interpretes spaces as a delimiter character. That is, if you are specifying an argument that consists of multiple words with spaces inbetween, you MUST group this with quotes.

For example, instead of

# mz eth0 -t udp sp=1, dp=80, p=00:11:22:33

you could either omit the spaces

# mz eth0 -t udp sp=1,dp=80,p=00:11:22:33

or, even more safe, use quotes:

# mz eth0 -t udp "sp=1, dp=80, p=00:11:22:33"

In order to monitor what's going on you can enable the verbose mode using the -v option. The opposite is the quiet mode (-q) which will keep Mausezahn absolutely quiet (except for error messages and warnings.)

Don't confuse the payload argument p=... with the padding option -p. The latter is used outside the quotes!

4.3   The automatic packet builder

An important argument is "-t" which invokes a packet builder. Currently there are packet builders for ARP, BPDU, CDP, IP, partly ICMP, UDP, TCP, RTP, DNS, and SYSLOG. (Additionally you can insert a VLAN tag or a MPLS label stack but this works independent of the packet builder.)

You get context specific help of every packet builder using the help keyword, such as:

# mz -t bpdu help
# mz -t tcp help

For every packet you may specify an optional payload. This can be done either via HEX notation using the payload (or short p) argument or directly as ASCII text using the -P option:

mz eth0 -t ip -P "Hello World"                           # ASCII payload
mz eth0 -t ip p=68:65:6c:6c:6f:20:77:6f:72:6c:64         # hex payload
mz eth0 -t ip "proto=89,                           \
               p=68:65:6c:6c:6f:20:77:6f:72:6c:64, \     # same with other
               ttl=1"                                    # IP arguments

Note: The raw link access mode only accepts hex payloads (because you specify everything in hex here.)

4.4   Packet count and delay

Per default only one packet is sent. If you want to send more packets then use the count option -c <count>. When count is zero then Mausezahn will send forever.

Per default Mausezahn sends at maximum speed (and this is really fast ;-)). If you don't want to overwhelm your network devices or have other reasons to send at a slower rate then you might want to specify a delay using the -d <delay> option.

If you only specify a numeric value it is interpreted in microsecond units. Alternatively, for easier use, you might specify units such as seconds sec or milliseconds msec. (You can also abbreviate this with s or m.)

Note: Don't use spaces between the value and the unit!

Here are typical examples:

Send infinite frames as fast as possible:

# mz -c 0  "aa bb cc dd ...."

Send 100,000 frames with a 50 msec interval:

# mz -c 100000  -d 50msec "aa bb cc dd ...."

Send infinite BPDU frames in a 2 second interval:

# mz -c 0 -d 2s -t bpdu conf

Note: Mausezahn does not support fractional numbers. If you want to specify for example 2.5 seconds then express this e. g. in milliseconds (2500 msec).

4.5   Source and destination addresses

As mnemonic trick keep in mind that all packets run from "A" to "B".

You can always specify source and/or destination MAC addresses using the -a and -b options, respectively. These options also allow keywords such as rand, own, bpdu, cisco, and others.

Similarily you can specify source and destination IP addresses using the -A and -B options, respectively. These options also support FQDNs (i. e. domain names) and ranges such as or Additionally (only) the source address supports the rand keyword (ideal for "attacks").

Note: When you use the packet builder for IP-based packets (e. g. UDP or TCP) then Mausezahn automatically cares about correct MAC and IP addresses (i. e. it performs ARP, DHCP, and DNS for you). But when you specify at least a single link-layer address (or any other L2 option such as a VLAN tag or MPLS header) then ARP is disabled and you must care for the Ethernet destination address for yourself.

5   Layer-2

5.2   ARP

Mausezahn provides a simple interface to the ARP packet. You can specify the ARP method (request|reply) and up to four arguments: sendermac, targetmac, senderip, targetip, or short smac, tmac, sip, tip.

By default an ARP reply is sent with your own interface addresses as source MAC and IP address, and a broadcast destination MAC/IP address.

Send a gratitious ARP (as used for duplicate IP detection):

mz eth0 -t arp

ARP cache poisoning:

mz eth0 -t arp "reply, senderip=, targetmac=00:00:0c:01:02:03, \

where by default your interface MAC address will be used as sendermac, senderip denotes the spoofed IP, targetmac and targetip identifies the receiver.

By default the Ethernet source address is your interface MAC and the destination address is broadcast. Of course you can change this using again the flags -a and -b.

5.3   BPDU

Mausezahn provides a simple interface to the 802.1d BPDU frame format (used to create the Spanning Tree in bridged networks).

By default standard IEEE 802.1d (CST) BPDUs are sent and it is assumed that your computer wants to become the root bridge (rid=bid).

Optionally the 802.3 destination address can be a specified MAC address, broadcast, own MAC, or Cisco's PVST+ MAC address. The destination MAC can be specified using the -b command which (besides MAC addresses) accepts keywords such as bcast, own, pvst, or stp (default).

Since version 0.16 PVST+ is supported. Simply specify the VLAN for which you want to send a BPDU:

mz eth0 -t bpdu "vlan=123, rid=2000"

See mz -t bpdu help for more details.

5.4   CDP

Mausezahn can send Cisco Discovery Protocol (CDP) messages since this protocol has security relevance. Of course lots of dirty tricks are possible; for example arbitrary TLVs can be created (using the hex-payload argument for example p=00:0e:00:07:01:01:90) and if you want to stress the CDP database of some device, Mausezahn can send each CDP message with another system-id using the change keyword:

# mz -t cdp change -c 0

Some routers and switches may run into deep problems ;-)

See mz -t cdp help for more details.

5.5   802.1Q VLAN Tags

Mausezahn allows simple VLAN tagging for IP (and other higher layer) packets. Simply use the option -Q <[CoS:]VLAN>, such as -Q 10 or -Q 3:921. By default CoS=0.

For example send a TCP packet in VLAN 500 using CoS=7:

mz eth0 -t tcp -Q 7:500 "dp=80, flags=rst, p=aa:aa:aa"

You can create as many VLAN tags as you want! This is interesting to create QinQ encapsulations or VLAN hopping:

# Send a UDP packet with VLAN tags 100 (outer) and 651 (inner)
mz eth0 -t udp "dp=8888, sp=13442" -P "Mausezahn is great" -Q 100,651

# Don't know if this is useful anywhere but at least it is possible:
mz eth0 -t udp "dp=8888, sp=13442" -P "Mausezahn is great"  \
        -Q 6:5,7:732,5:331,5,6

# Mix it with MPLS:
mz eth0 -t udp "dp=8888, sp=13442" -P "Mausezahn is great" -Q 100,651 -M 314

Only in raw Layer 2 mode you must create the VLAN tag completely by yourself. For example if you want to send a frame in VLAN 5 using CoS 0 simply specify 81:00 as type field and for the next two bytes the CoS (, CFI) and VLAN values:

mz eth0 -b bc -a rand "81:00 00:05 08:00 aa-aa-aa-aa-aa-aa-aa-aa-aa"

5.6   MPLS labels

Mausezahn allows you to insert one or more MPLS headers. Simply use the option -M <label:CoS:TTL:BoS> where only the label is mandatory. If you specify a second number it is interpreted as the experimental bits (the CoS usually). If you specify a third number it is interpreted as TTL. Per default the TTL is set to 255.

The Bottom of Stack flag is set automatically (otherwise the frame would be invalid) but if you want you can also set or unset it using the S (set) and s (unset) argument. Note that the BoS must be the last argument in each MPLS header definition.

Here are some examples:

# Use MPLS label 214
mz eth0 -M 214 -t tcp "dp=80" -P "HTTP..." -B

# Use three labels (the 214 is now the outer)
mz eth0 -M 9999,51,214 -t tcp "dp=80" -P "HTTP..." -B

# Use two labels, one with CoS=5 and TTL=1, the other with CoS=7
mz eth0 -M 100:5:1,500:7 -t tcp "dp=80" -P "HTTP..." -B

# Unset the BoS flag (which will result in an invalid frame)
mz eth0 -M 214:s -t tcp "dp=80" -P "HTTP..." -B

6   Layer 3-7

IP, UDP, and TCP packets can be padded using the -p option. Currently 0x42 is used as padding byte ('the answer'). You cannot pad DNS packets (would be useless anyway).

6.1   IP

Mausezahn allows you to send any (malformed or correct) IP packet. Every field in the IP header can be manipulated.

The IP addresses can be specified via the -A and -B options, denoting the source and destination address, respectively. You can also specify an address range or a host name (FQDN). Additionally, the source address can also be random.

By default the source address is your interface IP address and the destination address is a broadcast.

Here are some examples:

# ascii payload:
mz eth0 -t ip -A rand -B  -P "hello world"

# hex payload:
mz eth0 -t ip -A -B p=ca:fe:ba:be

# will use correct source IP address:
mz eth0 -t ip -B

The Type of Service (ToS) byte can either be specified directly by two hexadecimal digits (which means you can also easily set the Explicit Congestion Notification (ECN) bits (LSB 1 and 2) or you may only want to specify a common DSCP value (bits 3-8) using a decimal number (0..63):

# Packet sent with DSCP = Expedited Forwarding (EF):
mz eth0 -t ip dscp=46,ttl=1,proto=1,p=08:00:5a:a2:de:ad:be:af

If you leave the checksum zero (or unspecified) the correct checksum will be automatically computed. Note that you can only use a wrong checksum when you also specify at least one L2 field manually (because then the packet is not sent through the kernel).

6.2   UDP

Mausezahn support easy UDP datagram generation. Simply specify the destination address (-B option) and optionally an arbitrary source address (-A option) and as arguments you may specify the port numbers using the dp (destination port) and sp (source port) arguments and a payload.

You can also easily specify a whole port range which will result in sending multiple packets. Here are some examples:

Send test packets to the RTP port range:

mz eth0 -B -t udp "dp=16384-32767, \

Send a DNS request as local broadcast (often a local router replies):

mz eth0 -t udp dp=53,p=c5-2f-01-00-00-01-00-00-00-00-00-00-03-77-77-\

Additionally you may specify the lenght and checksum using the len and sum arguments (will be set correctly by default).

Several protocols have same arguments such as len (length) and sum (checksum). If you specified a udp type packet (via -t udp) and want to modify the IP length, then use the alternate keyword iplen and ipsum. Also note that you must specify at least one L2 field which tells Mausezahn to build everything without help of your kernel (the kernel would not allow to modify the IP checksum and the IP length).

6.3   ICMP

Mausezahn currently only supports the following ICMP methods:

  • PING (echo request)
  • Redirect (various types)
  • Unreachable (various types)

Additional ICMP types will be supported in future. Currently you would need to taylor them by your own, e. g. using the IP packet builder (setting proto=1).

Use the mz -t icmp help for help on actually implemented options.

6.4   TCP

Mausezahn allows you to easily taylor any TCP packet. Similar as with UDP you can specify source and destination port (ranges) using the sp and dp arguments.

Then you can directly specify the desired flags using an "|" as delimiter if you want to specify multiple flags. For example, a SYN-Flood attack against host using a random source IP address and periodically using all 1023 well-known ports could be created via:

mz eth0 -A rand -B -c 0 -t tcp "dp=1-1023, flags=syn"  \
        -P "Good morning! This is a SYN Flood Attack.          \
            We apologize for any inconvenience."

Be careful with such SYN floods and only use them for firewall testing. Check your legal position!

Remember that a host with an open TCP session only accepts packets with correct socket information (addresses and ports) and a valid TCP sequence number (SQNR). If you want to try a DoS attack by sending a RST-flood and you do NOT know the target's initial SQNR (which is normally the case) then you may want to sweep through a range of sequence numbers:

mz eth0 -A -B \
        -t tcp "sp=80,dp=80,s=1-4294967295"

Fortunately the SQNR must match the target host's acknowledgement number plus the announced window size. Since the typical window size is something between 40000 and 65535 you are MUCH quicker when using an increment using the ds argument:

mz eth0 -A -B \
        -t tcp "sp=80, dp=80, s=1-4294967295, ds=40000"

In the latter case Mausezahn will only send 107375 packets instead of 4294967295 (which results in a duration of approximately 1 second compared to 11 hours!).

Of course you can taylor any TCP packet you like. In future Mausezahn may support an automatic 3-way handshake.

As with other L4 protocols Mausezahn builds a correct IP header but you can additionally access every field in the IP packet (also in the Ethernet frame).

6.5   DNS

Mausezahn supports UDP-based DNS requests or responses. Typically you may want to send a query or an answer. As usual you can modify every flag in the header. Here is an example of a simple query:

./mz eth0 -B -t dns ""

You can also create server-type messages:

./mz eth0 -A -B \
                   ", a="

The syntax according to the online help (-t dns help) is:

query|q = <name>[:<type>]  ............. where type is per default "A"
                                         (and class is always "IN")

answer|a = [<type>:<ttl>:]<rdata> ...... ttl is per default 0.
         = [<type>:<ttl>:]<rdata>/[<type>:<ttl>:]<rdata>/...

Note: If you only use the 'query' option then a query is sent. If you additonally add an 'answer' then an answer is sent.


q =
q =, a=
q =, a=A:3600:
q =,

Please try out mz -t dns help to see the many other optional command line options.

6.6   RTP and VoIP path measurements

Mausezahn can send arbitrary Real Time Protocol (RTP) packets. Per default a classical G.711 codec (20 ms segment size, 160 bytes) is assumed.

You can measure jitter, packet loss and reordering along a path between two hosts running Mausezahn. The jitter measurement is either done following the variance low-pass filtered estimation specified in RFC 3550 or using an alternative "real-time" method which is even more precise (the RFC-method is used by default).

For example on Host1 you start a transmission process:

# mz -t rtp -B

And on Host2 ( a receiving process which performs the measurement:

# mz -T rtp

Note that the option flag with the capital "T" means that it is a server RTP process, waiting for incoming RTP packets from any Mausezahn source.

In case you want to restrict the measurement to a specific source or you want to perform a bidirectional measurement, you must specify a stream identifier.

Here is an example for bidirectional measurements which logs the running jitter average in a file:

Host1# mz -t rtp id=11:11:11:11 -B &
Host1# mz -T rtp id=22:22:22:22 "log, path=/tmp/mz/"

Host2# mz -t rtp id=22:22:22:22 -B &
Host2# mz -T rtp id=11:11:11:11 "log, path=/tmp/mz/"

In any case the measurements are printed continuously onto the screen; by default it looks like this:

0.00                     0.19                      0.38                      0.57
#########                                                                      0.07 msec
####################                                                           0.14 msec
##                                                                             0.02 msec
###                                                                            0.02 msec
#########                                                                      0.07 msec
####                                                                           0.03 msec
#########                                                                      0.07 msec
#############                                                                  0.10 msec
##                                                                             0.02 msec
###########################################                                    0.31 msec
#########                                                                      0.07 msec
##############################################                                 0.33 msec
###############                                                                0.11 msec
##########                                                                     0.07 msec
###############                                                                0.11 msec
##########################################################                     0.42 msec
#####                                                                          0.04 msec

More information is shown using the txt keyword:

# mz -T rtp txt
Got 100 packets from host 0 lost (0 absolute lost), 1 out of order
  Jitter_RFC (low pass filtered) = 30 usec
  Samples jitter (min/avg/max)   = 1/186/2527 usec
  Delta-RX (min/avg/max)         = 2010/20167/24805 usec

Got 100 packets from host 0 lost (0 absolute lost), 1 out of order
  Jitter_RFC (low pass filtered) = 17 usec
  Samples jitter (min/avg/max)   = 1/53/192 usec
  Delta-RX (min/avg/max)         = 20001/20376/20574 usec

Got 100 packets from host 0 lost (0 absolute lost), 1 out of order
  Jitter_RFC (low pass filtered) = 120 usec
  Samples jitter (min/avg/max)   = 0/91/1683 usec
  Delta-RX (min/avg/max)         = 18673/20378/24822 usec

See mz -t rtp help and mz -T rtp help for more details.

6.7   Syslog

The traditional Syslog protocol is widely used even in professional networks and is sometimes vulnerable. For example you might insert forged Syslog messages by spoofing your source address (e. g. impersonate the address of a legitime network device):

mz -t syslog sev=3 -P "You have been mausezahned." -A -B

See mz -t syslog help for more details.

7   Dear users

Mausezahn is still under heavy development and you may expect new features very soon.

Please report to herbert AT perihel DOT at regarding:

  • Bugs
  • Important features you miss
  • How you used Mausezahn (I am really interested in practical problems)
  • Interesting observations with Mausezahn at the network