Network PC World

Today, I successfully completed a lab in GNS3 to work with dot1x wired authentication. In my lab, I used Cisco IOU L2 Image , FreeRADIUS Servers for remote authentication and CentOS 7 as a Client operating system. In this post I will show my working configuration for Cisco L2 Switch, where " no ip routing " is configured. And a snapshot for from CentOS for network security setting to authenticate with 802.1x protocol. On switch I used following configurations My Cisco IOU L2 Image is ACCESS-SW# sh version | in  Version Cisco IOS Software, Solaris Software (I86BI_LINUXL2-IPBASEK9-M), Experimental Version 15.1(20130726:213425) [dstivers-july26-2013-team_track 105] ! ACCESS-SW# show run ! ! output only dot1x related configuration ! aaa new-model aaa group server radius RADIUS1  server name FreeRADIUS aaa authentication dot1x default group RADIUS1 local dot1x system-auth-control ! interface Ethernet3/0  switchport access vlan 10  switchport mode acce

Today, while working on a multicast lab on Cisco Router. I build a lab to send multicast stream from one end to other end via VLC. I found that, while checking router with " show ip mroute " command , receiver PC was successful registering with Rendezvous Point Server to receive required multicast traffic but the Multicast source (Sender) was not registering with RP. Upon a day's troubleshooting, i found in the packet capture that VLC Sender is sending multicast traffic with TTL Value 1, this is default behavior of VLC player and which will definitely be discarded by first receiving hop. So I have to increase the TTL value little higher so that the multicast packets can traverse to some hops and reach the receiver. To change the TTL value of the packet for sending multicast stream from VLC, you can change the default settings as per give below path and snap. I also tried this in GNS3 and was working fine. Go to Tools > Preferences >  Select ALL radio button

I am using GNS3 VM and connecting to it remotely from my laptop. I was facing an issue where telnet to GNS3 routers/switches stopped working, though required router or switch was working properly and passing traffic but somehow it was disconnecting the telnet session. This issue happened when I directly close the telnet session,  or when my laptop is locked/logged off and upon re-connecting to GNS3 VM, I was unable to take console session to the router/switch until i restart the particular router/switch. Solution to this problem was to properly " exit the console session with cli command " and not closing the putty window directly. Or you can configure your router/switch for console timeout after some time. 

[root@monitoring ~]#  snmpwalk -c public -v1 10.0.33.228 End of MIB I was trying to do snmwalk walk for a Cisco Router in GNS3, and was getting only End of MIB after a snmpwalk command.  It turned out that in my Cisco Router configurations I had allowed my SNMP host with ip address with community string "public" but I had not configured the community string separatly with the command  #snmp-server community public This was my configuration mistake but took some time to figure it out

Error while creating node: Docker has returned an error: Cannot connect to host docker:80 ssl:False [No such file or directory] After adding docker template for Alpine Linux in gns3, you get above mentioned message when you want to use alpine linux in GNS3. To get rid of this message you have to install Docker by following below link curl -fsSL https://get.docker.com/ | sh If you do not have curl installed then instal curl first with below command. apt-get install curl After installing Docker you need to add your user name in the docker group with the following command.  $ sudo usermod -aG docker your_username Verify if the docker service is started with following command $ service docker status If docker is not started then start with following command  $ sudo service docker start Logout from GNS3 Virtual Machines and log back. Start gns3 and use alpine linux.

Solution… 1. Go to Edit menu 2. Select Preferences\Dynmips 3. Uncheck “Automatically clean the work directory” By default it is enabled and once you close GNS3, your bootflash file is deleted. I have tried this and is working for me, hopefully will do for you too…

Most of us set idlepc value in GNS3 but do not really know the actual reason of setting it or what it does with CPU to stop its continuous process… Here is the brief explanation that why idlepc value is set in GNS3 When an IOS image is launched using Dynamips/GNS3 your PC will not be able to differentiate between the router’s real work and idle routines and so the router instance will use as much resource as possible, this becomes obvious when your CPU hits 100%. IdlePC is a value set locally that tells your computer when the router is idle or not and therefore when software needs to compute routines. It is set on a per-IOS image level, not router or host machine level which means values that are known to be good are valid on all GNS3/dynamips servers.

Probably you are using gns3 for the fist time and getting this problem! that when you make you topology, make all configurations, save it and when you restart the gns3 all the configurations are gone away, and only the topology diagram is there? Don’t worry it is because you are missing one step while saving your Router’s configurations in gns3, that is you have to export the configurations after that you have to save the gns3 file. Saving Router’s Configurations in gns3 is a two step process 1. Click the FILE menu and Click the import/Export, save the file where you want or choose the default location 2. Click the FILE menu and Click Save. Step are also shown in the Snap below, Please click to maximize it.

cannot start console applications: [WinError 2] The system cannot find the file specified. I got this error, upon checking I found that I had not installed wireshark during installing gns3. Installed wireshark separately and the error is gone. I did no configuration except installing wireshark.  I can see and capture traffic on gns3 device's interfaces by just right clicking any interface and then clicking "start wireshark".