Integrate Cisco CME in your lab with GNS3

Introduction :

You want to add a Cisco router with CME on your lab but you don’t have enough money to buy it.
You can use the router emulator GNS3 with a router IOS with CME integrated.

In this post, I summarize some information I used to build my proper lab. So I installed GNS3 on a Windows XP Virtual Machine and configure GNS3 and Windows XP in order to link the virtual CME to the lab Network.

Afterward it’s possible to add external IP Phones to the virtual CME or a SIP Trunk to a Cisco CUCM.

Schema :


Windows XP Configuration :

First of all, to link our virtual GNS3 Network to our real lab network we need to :

– Configure a loopback interface on windows XP

– Enable routing on windows XP

Windows XP Loopback configuration :

The loopback interface will be used on GNS3 for the configuration of the GNS3 cloud equipment. In this way, your Virtual GNS3 Network could be linked to your real lab network.

The following microsoft KB explains how to do :

Enable Routing on Windows XP :

We need to enable routing on our Windows XP server in order to forward packets between the virtual network and the real network.

The following microsoft KB explains how to enable routing :

GNS3 Configuration :

GNS3 Topology :


Don’t forget to fix an idle pc value to your router just after started it (right click -> idle pc) ! It’s important in GNS3, indeed without idle pc the router will consume all the CPU.

Router specification :

We are using a 3725 Router with an IOS c3725-adventerprisek9_ivs-mz.124-15.T9


For RAM and flash configuration


R2#show version
Cisco IOS Software, 3700 Software (C3725-ADVENTERPRISEK9_IVS-M), Version 12.4(15                                                                                                                     )T9, RELEASE SOFTWARE (fc5)
Technical Support:
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Tue 28-Apr-09 16:14 by prod_rel_team

ROM: ROMMON Emulation Microcode
ROM: 3700 Software (C3725-ADVENTERPRISEK9_IVS-M), Version 12.4(15)T9, RELEASE SO                                                                                                                     FTWARE (fc5)

R2 uptime is 22 minutes
System returned to ROM by unknown reload cause - suspect boot_data[BOOT_COUNT] 0                                                                                                                     x0, BOOT_COUNT 0, BOOTDATA 19
System image file is "tftp://"

This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

If you require further assistance please contact us by sending email to

Cisco 3725 (R7000) processor (revision 0.1) with 249856K/12288K bytes of memory.
Processor board ID FTX0945W0MY
R7000 CPU at 240MHz, Implementation 39, Rev 2.1, 256KB L2, 512KB L3 Cache
2 FastEthernet interfaces
DRAM configuration is 64 bits wide with parity enabled.
55K bytes of NVRAM.
32768K bytes of ATA System CompactFlash (Read/Write)

Configuration register is 0x2102

CME Version :

R2#show telephony-service
CONFIG (Version=4.1(0))
Version 4.1(0)
Cisco Unified Communications Manager Express
For on-line documentation please see:

External Links :

For more detailed information, you can consult the following excellent link :


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