The Keyboardbanger GNS3 Tutorial

Down below you have a complete list of my GNS3 ramblings during my CCNP Routing and Switching journey.

Useful Links to set up Cisco Switching Labs with GNS3

How to build a home Cisco switching lab with GNS3 and Ubuntu

How to Use Virtual PC Simulator in GNS3

Download Virtual PC Simulator

• You can download Virtual PC Simulator for free on the following URL: http://sourceforge.net/projects/vpcs/
• Click on the green download button to begin the download:

Router on a Stick configuration with GNS3 and VPCS

The Router on a Stick concept was introduced to me in my CCNA studies. This section demonstrates a quick example in GNS3 to understand the concept.

The purpose of the Router on a Stick is to use a router with a single physical interface and segment it into as many sub-interfaces as there are VLANs.

Suppose you have a switch with two vlans configured on it. Vlan A  and Vlan B. In each vlan you have a host. Let’s say host A and host B. In order for host A to talk to host B, you need a L3 device right? The simplest form is to have a router, with two physical interfaces: one in vlan A and the other in vlan B. But, what if we run out of physical interfaces on the router? Your boss tells you that you have to route between vlans and you have only one physical interface to do it. Here comes the stick! What you need to do is configure two subinterfaces on the router. Each subinterface will be tagged with either vlan A or vlan B (depending on your choice). So now, it’s as if you have a router with two interfaces, except that here they are logical and not physical.

Topology Router on a Stick sample topology

On my home lab, the router on which I configured the “Router on a Stick” feature is the “Gateway” router. The goal is to make PC1 (Payroll) communicate with PC2 (Engineering) through the “Gateway” router. Lab topology:

Here are our hosts, configured in two different VLANs. PC 1 has the IP address of 172.16.100.101/24 and PC2 has the IP address of 172.16.200.101/24:

A quick tracert from PC1 shows the inter-VLAN communication, thanks to the beautiful Router on a Stick.

How to Export and Import Configurations with GNS3 on Linux

GNS3 home lab on Windows

Here are my routers and their Putty sessions:

Here’s when I stopped the equipement:

By the way, GNS3 on Windows sucks! it crashes a lot of times. I recommend to go on Linux because it’s much more stable.

Calculating GNS3 idle PC value

GNS3 Waiting For http //127.0.0.1:8000 Error In Windows

In my GNS3 lab work, I often experience issues closing the program. It’s even annoying and sometimes a pain in the ass,

I’ve searched on the Internet for a while. I even thought about switching my whole lab to Linux. This won’t be a good idea for my CIPTV1 studies, because I have IP Blue and X-Lite softphones that only run on Windows. Besides, I have a couple of Virtualbox virtual machines that I’ve built delicately and whose transition to Linux won’t be easy.

I pinged the localhost IP address to see if I really can reach it:

Apparently, I was wrongly accusing GNS3. It seems there is a issue connecting to the 127.0.0.1. I remember from my past college days that network connectivity to 127.0.0.1 must be established to confirm that TCP/IP is correctly installed on the computer. So there must be something with the firewall.

I’m using Comodo Free firewall. Although you may think it’s not that good because it’s free, I find it great and easy to use.

I disabled Comodo firewall:

And I pinged 127.0.0.1 once again:

Now it works. I now confirm it’s a firewall issue. But I don’t want to disable my firewall altogether. I must create a security rule that allows IP traffic to 127.0.0.1. In Comodo firewall, you create a network zone and allow traffic to it.
Here’s how to do it in the GUI of Comodo firewall:

Defining the network zone for 127.0.0.1

Go to the main menu and click on Firewall

Go to Network Zones

In the network zone area, click on the bottom arrow:

then click on Add

Click on New Network Zone

Type the network zone name. I named it loopback Zone. Click OK

In the menu, select the loopback Zone network zone and click Add –> New Address

Select IPv4 Single Address and define the local loopback address 127.0.0.1.

click OK to commit the changes.

Defining the global rule that allows traffic to 127.0.0.1

Go to Firewall –> Global Rules

click on the bottom arrow then Add

Allow IP traffic, inbound and outbound. Name the firewall rule by giving it a description. And define the Source Address as “Any Address”:

In the “Destination Address” field, set the Type to Network Zone, and the zone to Loopback Zone:

In the IP Details field, set the IP Protocol to Any:

Click OK

Click OK to commit changes.

Switch the firewall back on.

If you did a continuous ping earlier and the ping did not fail after you commit the firewall changes, it means you established connectivity to 127.0.0.1 successfully through the firewall.

Testing the result by opening and closing GNS3

After all the customization made to your firewall, open your GNS3 file and close multiple times. Normally you will no longer encounter the “waiting for http://127.0.0.1:8000” error any more. And my computer no longer freezes when I close GNS3.

Another trick that can reduce your CPU utilization is by changing your hubs with a layer 3 switch. The trick works if you connected more than one device on a single hub.

Setting GNS3 Project Directory

When you use GNS3 and want to create a new project, the software asks you to choose a project directory. Sometimes, the path is not really what you wanted to project to be stored to. So here is the solution:

I’m going to set my default GNS3 project directory to the following: “Z:\GNS3 projects”

• In GNS3, go to Edit –> Preferences…

• click on the General tab at your upper left side
• Under Projects Directory, type the desired path in the text field. In my case, I type “Z:\GNS3 projects” (without the double quotes of course)

• Click Apply when finished.

Next time you launch a new GNS3 project and type a project name, it will be stored in your favourite project directory.

GNS3 Project Files

In the past, I had encountered some hard drive issues that led me to transfer my GNS3 project files to a thumbdrive. At first, I did not know what to copy and what to leave. Then I took a look at the project folder itself and counted the files one by one (like a mummy duck counts her baby ducks) so not to lose any of them.

As an example, let’s explore the project named “kbb lab1”.

When we explore the folder, we will find the following files:

• Configs: this is where your device configurations reside
• qemu-flash-drives: this one gets saved with each project you make, even if you don’t use Qemu-based images
• topology: this file has the “.net” extension. It lays out the network topology in a dynagen language.
• topology(.PNG): this is new. In the older GNS3 versions, I used to make a screenshots of my topologies. Now GNS3 automatically generates one for me. Cool.

That’s all. You have two folders and two files. Each time you want to move your GNS3 project, make sure you have all these files.

Erasing router configuration from a project

There are some decent .net files that we download from the Internet. This is my case. I downloaded a .net file to use it to review TSHOOT exam.
However, I have to build the configurations from scratch. So I need to erase them from the project.
1/ backup your configurations that sit under working directory
2/ delete the cfg file from the working directory
3/ start the device in GNS3.

Adding IOS Images in GNS3

This section describes the step-by-step process to configure GN3 IOS images on a Windows machine.

It is assumed that you have the latest GNS3 software and a couple of IOS images for Cisco routers.

A list of IOS images and the amount of needed RAM is given in the table below. Note that these RAM values are the minimum values that worked with my GNS3 installation.

Add an IOS Image to GNS3

In the following steps, we will add a Cisco 7200 IOS image to GNS3 and configure it.

• In the GNS3 menu bar, go to Edit
• Under the Edit menu, click on IOS Images and Hypervisors
• In Preferences, under Dynamips–> IOS routers, click on new:

• Browse to the folder which contains the desired IOS image. Select the desired IOS image and click the Open button (pardon my French keyboard)
• Click Yes to copy the IOS image to the default images directory:
  
• After you hit the save button, click Next. Then you’ll be taken to the menu for defining the name and the plateform of the IOS
• Choose adequate amount of RAM for the router:

• Continue with the steps until you finish creating an image.

Repeat the same steps for every IOS image you want to have in GNS3.

GNS3 High CPU Usage And Hubs

A couple of weeks ago I have been experiencing high CPU usage in my GNS3 home lab. After some trial and error, I localized the issue and discovered that the cloud device connection is the cause.

My old topology

I have a cloud device connected to a hub. The hub connects to the HQ router and the Unified Border Element. At some points in time, I hear the laptop fan working hard. This was not like that before adding the Unified Border Element. I think if you add more than two devices to a hub, your CPU will suffer.

So my old trick for this high CPU usage was to disconnect and re-connect the cloud device to the hub. However, one time out of three I get the gns3 waiting for http://127.0.0.1:8000 error. And my GNS3 setup crashes.

My new topology

I was thinking of getting rid of hubs. I tried a switch. But it did not establish connectivity between connected devices despite they were on the same vlan (GNS3 bug?)

Then I thought about putting a multilayer switch and doing the right routing configuration to make things work. So I had to segment the network into three subnets and route between them.

It did the job.

Not Enough Space On Flash To Store Vlan Database

You have installed GNS3, added a couple of IOS images and built a simple routing topology that includes a Cisco 3725 with an EtherSwitch NM-16ESW module. You start the router. You think about creating a vlan, and surprisingly see the following error:

I had this issue on my GNS3 home lab. I first tried to erase Flash but that showed an error message too:

Second, I changed the NVRAM size in the device configuration menu. This did not solve th eprobme either.

The solution is to change the PCMCIA Disk 0 size:

You see that it is initially set to 0 MB. So I change it to 1 MB:

Then I boot the router. It is now able to add vlans to its database:

Producing a Frame-Relay Topology in GNS3

You can reproduce this topology -and its configuration- for your CCNP Routing&Switching or CCNP Collaboration studies on GNS3.

A lot of CCNP’s like me remember this famous topology from the old BSCI exam. In the new CCNP Routing&Switching syllabus, frame relay has been wiped out.

Frame Relay Topology Example

We’re going to use this topology:

And the logical topology in terms of frame relay DLCI circuits is the following:

 PSTN router has three DLCIs:

• DLCI 401 with HQ router
• DLCI 402 with BR1 router
• DLCI 403 with BR2 router

The other routers connect to the frame relay networks as follows:

• HQ router has DLCI 101
• BR1 router has DLCI 102
• BR2 router has DLCI 103

In this topology:

• Traffic from any router goes through PSTN router before it reaches its final destination. It’s a hub-and-spoke topology; PSTN router is the hub, the remaining routers are the spokes.

IOU Unsupported Features in GNS3

Here is a list of Cisco IOU unsupported features that you probably won’t find, when labbing using Eve-NG or GNS3. The missing features were found with i86bi-linux-l2-adventerprise-15.1b.bin image. But the same observations could be true for other versions too.

My home lab IOU version is i86bi-linux-l2-adventerprise-15.1b.bin.

Policy-based routing with IP SLA tracking based on ICMP Echo

We can configure the Cisco IOS PBR -aka Policy-Based-Routing- with a special set ip next-hop value.

When we want to incorporate the tracking object within the Cisco IOS PBR, the track object can track an IP SLA operation.

When you track an IP SLA ICMP Echo on a Cisco IOU image switch, you get nothing. This is unsupported. Here is an example of an ICMP Echo IP SLA:

 DLS-1#sh ip sla configuration 5
 IP SLAs Infrastructure Engine-III 
 Entry number: 5
 Owner: Tag: Operation timeout (milliseconds): 5000
 Type of operation to perform: icmp-echo 
 Target address/Source address: 11.11.11.10/11.11.11.9 
 Type Of Service parameter: 0x0 
 Request size (ARR data portion): 28
 Data pattern: 0xABCDABCD Verify data: No 

I have invoked this IP SLA in a route map. A show route-map shows that the track object is down.

DLS-1#sh route-map RmapPBR
route-map RmapPBR, permit, sequence 10 
Match clauses: 
ip address (access-lists): PBRacl1 
Set clauses: 
ip next-hop verify-availability 11.11.11.10 1 track 55 [down] 
Policy routing matches: 0 packets, 0 bytes 
DLS-1# 

But the reality is that the track object is not getting any feedback from the ICMP Echo IP SLA. Even a show track gives no useful information about the state or the reachability of the IP SLA operation:

 DLS-1#sh track 55 Track 55
 IP SLA 5 state 
 State is Down 
 1 change, last change 00:12:58 
 Latest operation return code: Unknown 
 Tracked by: 
  Route Map 0 

However, tracking IP SLA ICMP Echo with a simple host, such as VPCS, works:

 DLS-1>sh ip sla summ
 IPSLAs Latest Operation Summary 
 Codes: * active, ^ inactive, ~ pending 
 ID   Type    Destination Stats     Return     Last 
                           (ms)      Code       Run 
----------------------------------------------------------------------- 
*2     icmp-echo    172.16.200.101 RTT=6 OK 49 seconds
ag !!! 172.16.200.101 is the IP address of a VPCS host. 

So what is the solution? use object tracking with UDP Echo IP SLA, not ICMP Echo.

DLS-1>sh ip sla summ
IPSLAs Latest Operation Summary
Codes: * active, ^ inactive, ~ pending

ID           Type        Destination       Stats       Return      Last
                                           (ms)        Code        Run
-----------------------------------------------------------------------
*2           icmp-echo   172.16.200.101    RTT=6       OK          49 seconds ag
                                                                   o



*3           udp-echo    11.11.11.10       RTT=33      OK          9 seconds ago  !!!! 11.11.11.10 is the IP address of a SVI on a switch running Cisco IOU

LLDP

LLDP is not supported in Cisco IOU i86bi-linux-l2-ipbasek9-15.1e:

MLS(config)#lldp run
^
% Invalid input detected at '^' marker.

MLS(config)#

And it is indeed supported in Cisco IOU i86bi-linux-l3-adventerprisek9-15.2:

Router(config)#lldp run
Router(config)#

and in Cisco virtual IOS vios_l2-ADVENTERPRISEK9-M), Experimental Version 15.2:

DLS-2(config)#lldp ?
  holdtime    Specify the holdtime (in sec) to be sent in packets
  reinit      Delay (in sec) for LLDP initialization on any interface
  run         Enable LLDP
  timer       Specify the rate at which LLDP packets are sent (in sec)
  tlv-select  Selection of LLDP TLVs to send

LLDP on etherchannel interfaces

Cisco IOU vios_l2-ADVENTERPRISEK9-M), Experimental Version 15.2 does not support LLDP over Etherchannel ports.
Although we can see an exchange of LLDP packets, no LLDP neighbors are discovered on the ALS-2 switch:

Sep 26 10:52:38.661: LLDP advertisement packet TX'd on intf GigabitEthernet1/2
Sep 26 10:52:39.114: LLDP advertisement packet TX'd on intf GigabitEthernet0/0
Sep 26 10:52:39.297: LLDP advertisement packet TX'd on intf GigabitEthernet0/1
 --More--
Sep 26 10:52:49.120: LLDP advertisement packet RX'd on intf Port-channel2
Sep 26 10:52:49.425: LLDP advertisement packet RX'd on intf Port-channel2
 --More--
Sep 26 10:53:03.736: LLDP advertisement packet TX'd on intf GigabitEthernet0/2
 --More--
Sep 26 10:53:06.688: LLDP advertisement packet TX'd on intf GigabitEthernet0/3
 --More--
Sep 26 10:53:08.535: LLDP advertisement packet TX'd on intf GigabitEthernet1/2
Sep 26 10:53:08.979: LLDP advertisement packet TX'd on intf GigabitEthernet0/0
Sep 26 10:53:09.087: LLDP advertisement packet TX'd on intf GigabitEthernet0/1
 --More--
Sep 26 10:53:18.853: LLDP advertisement packet RX'd on intf Port-channel2
Sep 26 10:53:19.079: LLDP advertisement packet RX'd on intf Port-channel2

——————–

ALS-2#sh lldp nei
Capability codes:
    (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
    (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID           Local Intf     Hold-time  Capability      Port ID

Total entries displayed: 0

ALS-2#sh lldp nei
Capability codes:
    (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
    (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID           Local Intf     Hold-time  Capability      Port ID

Total entries displayed: 0

The home lab Etherchannel interface contains two member ports: gi0/0 and g0/1.
When I disabled then enabled LACP on one interface, LLDP suddenly found one neighbor on it:

ALS-2(config)#int gi0/1
ALS-2(config-if)#no channel-group 2 mod act
ALS-2(config-if)#channel-group 2 mod act
ALS-2(config-if)#end

ALS-2#sh lldp neighbors
Capability codes:
    (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
    (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID           Local Intf     Hold-time  Capability      Port ID
DLS-1               Gi0/1          120        R               Gi0/3

Total entries displayed: 1

I did the same thing with the second member port of the Etherchannel. I disabled then enabled LACP on gi0/0:

ALS-2(config)#int gi0/0
ALS-2(config-if)#no channel-group 2 mod act
ALS-2(config-if)#channel-group 2 mod act
ALS-2(config-if)#end
 !!! waiting a couple of seconds
ALS-2#sh lldp nei
Capability codes:
    (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
    (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID           Local Intf     Hold-time  Capability      Port ID
DLS-1               Gi0/0          120        R               Gi0/2
DLS-1               Gi0/1          120        R               Gi0/3

Total entries displayed: 2

However this situation lasts not long. As soon as we start seeing LLDP neighborship, we lose them again.

ALS-2#sh lldp nei
Capability codes:
    (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
    (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID           Local Intf     Hold-time  Capability      Port ID
DLS-1               Gi0/0          120        R               Gi0/2

Total entries displayed: 1

ALS-2#sh lldp nei
Capability codes:
    (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device
    (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other

Device ID           Local Intf     Hold-time  Capability      Port ID

Total entries displayed: 0

UDLD

UDLD is supported in Cisco vIOS though.

Switchport mode dynamic desirable

Switch-1(config-if)#switchport mode ?
  access        Set trunking mode to ACCESS unconditionally
  dot1q-tunnel  set trunking mode to TUNNEL unconditionally
  private-vlan  Set private-vlan mode
  trunk         Set trunking mode to TRUNK unconditionally

IP DHCP Snooping trust

It is possible with IOL to configure the IP DHCP Snooping feature. However, during the configuration of trust settings under the interface, this was not possible.
Cisco vIOS however does support it.

GLBP

Switch-3(config-if)#glb?
% Unrecognized command
Switch-3(config-if)#glb

Not only GLBP is not supported neither on Cisco IOU, nor on Cisco vIOS, but also don’t use IOU or vIOS when they are connecting to two GLBP routers. In fact, no GLBP protocol packets are exchanged over IOU/vIOS.
To circumvent that, I simply use a normal hub in EVE-NG: Add a New Object –> Network.

HSRP

To circumvent this lacking feature, one can use Cisco 7200 IOS images. But these ones do not support HSRP Interface Tracking feature.

List of missing switch features on GNS3

GNS3 Unsupported Commands on NM-16ESW

Installing CallManager Express in GNS3

This section describes how to transform a Cisco router in GNS3 into a Cisco CallManager Express or CUCME.

Remember that a Cisco router can become a CallManager Express if we install the CUCME package into it.

I’ll assume you have a CUCME package on your computer.

Here is the setup in GNS3:

• a router destined to become CUCME
• a cloud item associated to the physical network card of the host machine
• a link between the router and the cloud.

We also need a TFTP server software. One of the best free TFTP servers is TFTPD32.

After you build the topology in GNS3, configure the router:

• set up the FastEthernet interface for connectivity with the host machine network. The host machine NIC address is 10.11.14.2. The router’s FastEthernet IP address is 10.11.14.254:

• Erase the router Flash:

• And format it:

To the TFTP server now. Download and install the TFTP server.

Set it up in a way that it points to a directory that contains the CUCME file.

On the GNS3 router, with the archive command:

• copy the CUCME tar file from the TFTP server to Flash,
• extract the files from the CUCME tar file.

After the operation terminates, you do a show telephony-service to display the CUCME version:

Connecting CUCM to GNS3

• a VM on which CUCM is running
• Vmware bridged networking technology: this feature allows CUCM network card to be on the same physical network as the host network card. This means we’ll have CUCM and our physical machine on the same subnet.
• GNS3 with one router and one cloud