Error – Failed to open a session for the virtual machine GNS3 VM

You may be prompted with the following error below when you wish to start a VM that the .vdi files have been deleted.

Expanding “details”, more insight of the error will be described. This error is self explanatory, therefore, I will proceed with the my recommendations (solutions) below.

– Restore the deleted .vdi files and attach it to the GNS3 VM
– Delete the GNS3 VM from Oracle Virtualbox and deleted all associated files and have a new GNS3 VM recreated.

See the video below if this might be helpful šŸ˜‰

How to Activate (License) Cisco ASA 5505

A license specifies the functionalities (options) that are enabled on a given ASA. It is represented by an activation key which is a 160-bit (5 32-bit words or 20 bytes) value. This value encodes the serial number (an 11 character string) and the enabled features. Below are the steps I followed to license Cisco ASA 5505

TestASA# show activation-key ?
detail Show activation-key details
   | Output modifiers
TestASA# show activation-key 
Serial Number:  JxxxxxxxxV
Running Permanent Activation Key: 0x0xxxx 0x94xxxx 0xf0xxxx 0xaxxxx1c 0x4xxxx0

Now that you have the serial number and the current running activation key, enter this information on the licensing website

Note: After obtaining the license it should look this way.

TestASA(config)# activation-key 27xxxxxc 4cxxx 1xxxx44 exxxx44 8fxxx8
Validating activation key. This may take a few minutes.

WARNING: AnyConnect Essentials license active. Basic VPN support is in effect. For specific details, please refer to Cisco AnyConnect VPN
Client Administrator Guide.

Both the Running and Flash permanent activation key was updated with the requested key and will become active after the next reload.

TestASA(config)# wr
Building configurationā€¦
Cryptochecksum: bxxxx5 ebxxxc6f f6xxxx0b fxxxxx2 
9360 bytes copied in 1.130 secs (9360 bytes/sec)

This platform has a Base license. The flash permanent activation key is the SAME as the running permanent key.

TestASA(config)# reload
Proceed with reload? [confirm] 


How to make a router function as a switch in GNS3

In order to achieve this in GNS3, follow the following steps below.

-Drag your router into the topology
– Right click on it and choose “configure
– Go over to the “slots” tab
– Leave the “slot 0” the way it is
– Make a “slot 1” entry for “NM-16ESW”, apply and save your changes
– Change the symbol on it to look like a switch if you want
– Enter the “no ip route” command in global config mode so it doesn’t act like a router

Switch_Router(config)#no ip routing
Switch_Router(config)#do copy run start

Note the following deviations from a normal switch config.
Switch# show vlan-switch
Switch# vlan database

Troubleshooting Cisco ASA -Commands

Use “show switch vlan” to view the vlans that have been assigned to Layer 2 switch ports.

 TestASA(config)# show switch vlan
 VLAN Name                             Status    Ports
 1    inside                           up        Et0/1, Et0/2, Et0/3, Et0/4
                                                 Et0/5, Et0/6, Et0/7
 2    outside                          down      Et0/0

Use the show int IP brief to view the configured interfaces

TestASA(config)# show int ip brief
Interface IP-Address OK? Method Status Protocol
Ethernet0/0 unassigned YES unset down down
Ethernet0/1 unassigned YES unset up up

Note on a cisco switch its “show ip interface brief”

use the show ip add a command to view the configured IP address of the interfaces and VLANs

TestASA(config)# show ip add
System IP Addresses:
Interface Name IP address Subnet mask Method
Vlan1 inside 192.1xx.1xx.xx CONFIG
Current IP Addresses:
Interface Name IP address Subnet mask Method
Vlan1 inside 192.1xx.1xx.xx CONFIG

To display the configured http server if configured

TestASA(config-if)# show run http
http server enable
http inside

To display the configured Telnet connection

TestASA(config)# show run telnet
telnet inside
telnet timeout 1000

To display the configured ssh connection

TestASA(config)# show run ssh
ssh stricthostkeycheck
ssh inside
ssh timeout 10

SG300 Firmware Upgrade – Copy: Illegal software format

When I had this error, some articles suggested that you need to install the upgrade the boot loader first before attempting the firmware upgrade. That the Boot loader (.rfb file) can be found on the same zip folder as the firmware. This does not work in this case.

What is a Firmware? A firmware is software that is embedded on the router.This firmware is normally updated to include new features and enhancements to the device. All of our firmware upgrades are FREE.

Solution: The steps below fixed the issue.
– All that needs to be done to correct this issue is to perform an interim firmware upgrade to the previous version. Then upgrade form this version to the next, till it gets to the most recent one.

The switch flash file system was changed in

How to wipe configuration off an interface on a Cisco router

The following command can be used to clear of the configuration on an interface on a Cisco Router or Switch

Switch(config)#default interface range gigabitethernet 0/1 - 52

Note: You can also use the negation command, by adding “no” before the command to clear off configuration applied to an interface or Cisco Switches and Routers

Disable Spanning-Tree Globally

Note: It is not recommended to turn STP off. There is no global command to disable spanning tree globally. But, you can disable all configured VLAN by “no spanning-tree vlan 1(that is on an individual vlan basis) or (have this done in range as shown below. vlan 1 – vlan50)

switch7(config)#no spanning-tree vlan 11-15

Now run the commands below to ensure spanning-tree is disabled for the vlans.

switch7#sh span
No spanning tree instance exists.

or use the full command as shown below

switch7#sh spanning-tree
No spanning tree instance exists.

Note: Only turn off spanning-Tree for the configured vlans on the switch.