DYNAMIPS(1)

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💖 dynamips(1) — General Commands Manual 💖

okay bestie, sit DOWN, because we're about to talk about dynamips, and this one is a whole personality. it's the Cisco router simulator, and it's lowkey iconic.

✨ NAME ✨

dynamips — Cisco router simulator 🫶

🌸 SYNOPSIS 🌸

dynamips [options] ios_image

🦋 DESCRIPTION 🦋

so basically, dynamips emulates Cisco routers on a traditional PC. you can use it to create labs. it runs on real Cisco IOS images, and heads up: those images are not included in this package. also, real talk — this emulator cannot replace a real router. it's simply a complementary tool to real labs, for administrators of Cisco networks or for people who want to pass their CCNA/CCNP/CCIE exams. it's giving study buddy, not study replacement 💅

the emulator currently supports the Cisco 7200, Cisco 3745, Cisco 3725, Cisco 3600, Cisco 2691, Cisco 2600, and Cisco 1700 series.

by default, a Cisco 7206VXR with NPE-200 (256 Mb of DRAM) is emulated. to emulate another platform — like the Cisco 3600 series — use the -P command line option. you can change the chassis type with -t. and bestie, do not forget to set it depending on your IOS image: a c3660 image will not run on c3640 hardware and vice-versa. they are not interchangeable, periodt.

✨ OPTIONS ✨

a summary of options is included below.

  • -H <tcp_port> — enable hypervisor mode. the hypervisor mode of dynamips lets you run simultaneously many virtual router instances, and to simulate ATM, Ethernet or Frame-Relay networks. you can connect directly to the TCP control port with telnet, or use dynagen(1), dynagui(1) which will pass commands transparently. the second method is highly recommended. 🫶
  • -l <log_file> — set logging file (default is dynamips_log.txt)
  • -j — disable the JIT compiler. it's very slow. like, we're talking snail energy 😭
  • --exec-area <size> — set the exec area size (default: 64 Mb). the exec area is a pool of host memory used to store pages translated by the JIT — they contain the native code corresponding to MIPS code pages.
  • --idle-pc <pc> — set the idle PC (default: disabled). the "idle PC" feature lets you run a router instance without having a 100% CPU load. this implies that you can run a larger number of instances per real machine. 🔥

to determine the "idle PC", start normally the emulator with your Cisco IOS image, and a totally IOS empty configuration (although not mandatory, this will give better results). when the image is fully booted, wait for the Press RETURN to get started! message prompt, but do not press the Enter key. wait about 5 seconds, then press Ctrl-] + i. some statistics will be gathered during 10 seconds. at the end, the emulator will display a list of possible values to pass to the --idle-pc option. you may have to try some values before finding the good one. to check if the idle PC value is good, just boot the Cisco IOS image, and check your CPU load when the console prompt is available. if it's low, you have found a good value — keep it preciously. 💎

important remarks, bestie, don't skip these: - an "idle PC" value is *specific* to a Cisco IOS image. you cannot boot a different IOS image without proceeding as described above. - do not run the process while having the "autoconfiguration" prompt.
  • --timer-itv <val> — Timer IRQ interval check (default: 1000)
  • -i <instance> — set instance ID
  • -r <ram_size> — set the virtual RAM size (default: 256 Mb)
  • -o <rom_size> — set the virtual ROM size (default: 4 Mb)
  • -n <nvram_size> — set the NVRAM size (default: 128 Kb)
  • -c <conf_reg> — set the configuration register (default: 0x2102)
  • -m <mac_addr> — set the MAC address of the chassis (default: automatically generated)
  • -C, --startup-config <file> — import IOS configuration file into NVRAM
  • --private-config <file> — import IOS configuration file into NVRAM
  • -X — do not use a file to simulate RAM (faster) ⚡
  • -R <rom_file> — load an alternate ROM (default: embedded)
  • -k <clock_div> — set the clock divisor (default: 4). specify the clock divider (integer) based on the host clock. alter the value to match the CISCO clock with the real time. the command show clock at the IOS' CLI will help you set this value.
  • -T <port> — console is on TCP <port>
  • -U <si_desc> — console is on serial interface <si_desc> (default is on the terminal)
  • -A <port> — AUX is on TCP <port>
  • -B <si_desc> — AUX is on serial interface <si_desc> (default is no AUX port)
  • --disk0 <size> — set PCMCIA ATA disk0: size (default: 64 Mb)
  • --disk1 <size> — set PCMCIA ATA disk1: size (default: 0 Mb)
  • -a <cfg_file> — Virtual ATM switch configuration file.
  • -f <cfg_file> — Virtual Frame-Relay switch configuration file.
  • -E <cfg_file> — Virtual Ethernet switch configuration file.
  • -e — show network device list of the host machine. 👀

🎀 OPTIONS specific to the Cisco 7200 series 🎀

  • -t <npe_type> — select NPE type (default: "npe-200")
  • -M <midplane> — select Midplane ("std" or "vxr")
  • -p <pa_desc> — define a Port Adapter
  • -s <pa_nio> — bind a Network IO interface to a Port Adapter

🌈 OPTIONS specific to the Cisco 3600 series 🌈

  • -t <chassis_type> — select Chassis type (default: "3640")
  • -p <nm_desc> — define a Network Module
  • -s <nm_nio> — bind a Network IO interface to a Network Module

💜 Cisco 7200 Port Adapter Description <pa_desc> 💜

Format: slot:pa_driver

  • slot — the number of the physical slot (starts from 0)
  • pa_driver — the name of a Port Adapter driver in:
    • C7200-IO-FE — (FastEthernet, slot 0 only)
    • PA-FE-TX — (FastEthernet, slots 1 to 6)
    • PA-4E — (Ethernet, 4 ports)
    • PA-8E — (Ethernet, 8 ports)
    • PA-4T+ — (Serial, 4 ports)
    • PA-8T — (Serial, 8 ports)
    • PA-A1 — (ATM)

🧚 Cisco 3600 Network Module Description <nm_desc> 🧚

Format: slot:nm_driver

  • slot — the number of the physical slot (starts from 0)
  • nm_driver — the name of a Network Module driver in:
    • NM-1E — (Ethernet, 1 port)
    • NM-4E — (Ethernet, 4 ports)
    • NM-1FE-TX — (FastEthernet, 1 port)
    • NM-4T — (Serial, 4 ports)
    • Leopard-2FE — (Cisco 3660 FastEthernet in slot 0, automatically used)

⭐ NIO binding to Port Adapter <pa_nio> and Network Modules <nm_nio> : ⭐

Format: slot:port:netio_type[:netio_parameters]

  • slot — the number of the physical slot (starts from 0)
  • port — the port in the specified slot (starts from 0)
  • netio_type — host interface for communication:
    • unix:<local_sock>:<remote_sock> — use unix sockets for local communication. <local_sock> is created and represents the local NIC. <remote_sock> is the file used by the other interface. (ex. "/tmp/local:/tmp/remote")
    • vde:<control_sock>:<local_sock> — for use with UML (User-Mode-Linux) or VDE switches. VDE stands for "Virtual Distributed Ethernet". please refer to : http://sourceforge.net/projects/vde/
    • tap:<tap_name> — use a virtual ethernet device for communication. <tap_name> is the name of the tap device (ex. "tap0")
    • gen_eth:<dev_name> — use a real ethernet device for communication, using libpcap 0.9 or WinPcap. works on Windows and Unix systems. <dev_name> is the name of the Ethernet device (ex. "eth0"). the device list can be found using the -e option.
    • linux_eth:<dev_name> — use a real ethernet device for communication (Linux specific). <dev_name> is the name of the Ethernet device (ex. "eth0")
    • udp:<local_port>:<remote_host>:<remote_port> — use an UDP socket for connection between remote instances. <local_port> is the port we listen to. <remote_host> is the host listening the port you want to connect to. <remote_port> is the port you want to connect to. (ex. "1000:somehost:2000" and "2000:otherhost:1000" on the other side)
    • tcp_cli:<host>:<port> — client side of a tcp connection. <host> is the ip address of the server. <port> is the port to connect to.
    • tcp_ser:<port> — server side of a tcp connection. <port> is the port to listen to.
    • null — dummy netio (used for testing/debugging), no parameters needed.

🍓 VTTY binding to real serial port device <si_desc> 🍓

Format: <device>{:baudrate{:databits{:parity{:stopbits{:hwflow}}}}}}

  • device — character device name, e.g. /dev/ttyS0
  • baudrate — baudrate
  • databits — number of databits
  • parity — data parity: N=none, O=odd, E=even
  • stopbits — number of stop bits
  • hwflow — hardware flow control (0=disable, 1=enable)

note that the device field is mandatory, however other fields are optional. (dynamips will default to 9600, 8, N, 1, no hardware flow control).

note that access to the escape commands (described below) through a serial port are deliberately prevented, as the escape commands interfere with serial encapsulation protocols. 🫶

👑 Escape commands 👑

you can press ^] (Ctrl + ]) at any time, followed by one of these characters:

  • o — show the VM object list
  • d — show the device list
  • r — dump MIPS CPU registers
  • t — dump MIPS TLB entries
  • m — dump the latest memory accesses
  • s — suspend CPU emulation
  • u — resume CPU emulation
  • q — quit the emulator
  • b — dump the instruction block tree
  • h — JIT hash table statistics
  • l — MTS64 cache statistics
  • c — write IOS configuration to disk (ios_cfg.txt)
  • j — non-JIT mode statistics
  • x — experimentations (can crash the box! 💀)
  • ^] — send ^]

if you press an unrecognized key, help will be shown. note: on Windows, it may be the "Ctrl + $" sequence.

💖 Virtual Bridge 💖

okay bestie so the virtual bridge is literally here to emulate a shared network between emulator instances. and the tea is: any emulator instance can act as a virtual bridge. no cap. 🫶

The config file (you specify it with the -b option) has a list of NetIO descriptors, and the syntax is giving:

interface_name:netio_type[:netio_parameters]

Example, periodt:

# Connection to instance "I0"
I0:udp:10000:127.0.0.1:10001
# Connection to instance "I1"
I1:udp:10002:127.0.0.1:10003
# Connection to instance "I2"
I2:udp:10004:127.0.0.1:10005

So the "I0" instance would be launched with these exact params:

dynamips ios.bin -p 1:PA-FE-TX -s 1:0:udp:10001:127.0.0.1:10000

🌈 Virtual Ethernet switch 🌈

The virtual ethernet switch is used to emulate an Ethernet network between emulator instances. and yes it supports access and trunk ports (802.1Q). ISL will be available in a future release (so not yet, bestie). Any emulator instance can act as a virtual ethernet switch.

The config file (you specify it with the -E option) contains a list of NetIO descriptors (representing interfaces) and a list of interface properties (access/trunk port, VLAN info...). The interface definition is similar to Port Adapters:

IF:interface_name:netio_type[:netio_parameters]

Access Port

ACCESS:interface_name:vlan_id

802.1Q Trunk Port

DOT1Q:interface_name:native_vlan

The native VLAN is not tagged. On Cisco devices, by default the native VLAN is VLAN 1.

Example of configuration file:

IF:E0:udp:10000:127.0.0.1:10001
IF:E1:udp:10002:127.0.0.1:10003
IF:E2:gen_eth:eth0
DOT1Q:E0:1
ACCESS:E1:4
DOT1Q:E2:1

🦋 Virtual ATM switch 🦋

The virtual ATM switch fabric is used to emulate an ATM backbone between emulator instances. The use of this virtual switch is not mandatory, you can directly connect emulator instances for point-to-point ATM connections. Please note that only basic VP/VC switching is supported, there is no support for ILMI/QSAAL/... or other specific ATM protocols. Any emulator instance can act as a virtual ATM switch.

Example of configuration file (specified by the -a option):

# Virtual Interface List
IF:A0:udp:10001:127.0.0.1:10000
IF:A1:udp:10002:127.0.0.1:10003
IF:A2:udp:10004:127.0.0.1:10005
# VP connection between I0 and I1
VP:A0:10:A1:20
VP:A1:20:A0:10
# VP connection between I0 and I2
VP:A0:11:A2:30
VP:A2:30:A0:11
# VC connection between I1 and I2
VC:A1:5:2:A2:7:3
VC:A2:7:3:A1:5:2

In this example, we have 3 virtual interfaces, A0, A1 and A2. The syntax for interface definition is similar to Port Adapters:

IF:interface_name:netio_type[:netio_parameters]

You can do VP switching or VC switching:

VP switching

VP:input_if:input_vpi:output_if:output_vpi

VC switching

VC:input_if:input_vpi:input_vci:output_if:output_vpi:output_vci

✨ Testing the Virtual ATM switch with one dynamips instance ✨

Virtual ATM switch configuration file ("atm.cfg"):

IF:A0:udp:10003:127.0.0.1:10001
IF:A1:udp:10004:127.0.0.1:10002
# a0/vpi=1/vci=100 connects to a1/vpi=2/vci=200
VC:A0:1:100:A1:2:200
VC:A1:2:200:A0:1:100

Invoking dynamips:

./dynamips -p 1:PA-A1 -s 1:0:udp:10001:127.0.0.1:10003 -p 2:PA-A1
-s 2:0:udp:10002:127.0.0.1:10004 -a atm.cfg IOS.BIN
(note input ports of IOS interfaces are output ports of ATM switch interfaces, and vice versa).

IOS Configuration:

ip cef
ip vrf test
 rd 1:1
 route-target both 1:1
int a1/0
 no shut
int a1/0.2 p
 ip addr 1.1.1.1 255.255.255.0
 pvc 1/100
interface a2/0
 no shut
interface a2/0.2 p
 ip vrf forwarding test
 ip addr 1.1.1.2 255.255.255.0
 pvc 2/200
!

🎀 Virtual Frame-Relay switch 🎀

The virtual Frame‐Relay switch fabric is used to emulate a Frame‐Relay backbone between emulator instances. The use of this virtual switch is not mandatory, you can directly connect emulator instances with appropriate IOS configuration. Any emulator instance can act as a virtual Frame‐Relay switch. There is only a basic implementation of the LMI protocol (ANSI Annex D), which is probably not conforming but works with Cisco IOS. Fortunately, Cisco IOS is able to detect automatically the LMI protocol.

Example of configuration file (specified by the -f option):

# Virtual Interface List
IF:S0:udp:10001:127.0.0.1:10000
IF:S1:udp:10002:127.0.0.1:10003
# DLCI switching between S0 and S1
VC:S0:200:S1:100
VC:S1:100:S0:200

In this example, we have 2 virtual interfaces, S0 and S1. The syntax for interface definition is similar to Port Adapters:

IF:interface_name:netio_type[:netio_parameters]

DLCI switching syntax:

VC:input_if:input_dlci:output_if:output_dlci

In the example above, the switch is configured to switch packets received on interface S0 with DLCI 200 to interface S1 with DLCI 100, and vice‐versa.

💀 BUGS 💀

See RELEASE-NOTES.

😭 REPORTING BUGS 😭

Please send bug reports to https://github.com/GNS3/dynamips/issues

👑 SEE ALSO 👑

🌸 OLD WEBSITES 🌸

💜 AUTHOR 💜

dynamips is being maintained by Flávio J. Saraiva <flaviojs2005@gmail.com>. This manual page was initially written by Erik Wenzel <erik@debian.org> for the Debian GNU/Linux system.

And that's the tea! This was DYNAMIPS(1), version from Sep 28, 2013. Stay iconic, bestie. 💖

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