2950 SWITCH receive config file from ISP ?!?

[Didier1966]

Hello,

At home I have a perfectly working test setup for more than 1 year now , but yesterday we had a power down for about 10 minutes in the whole area , after this power down nothing was working in my network any longer.

My Network is has follow :

ISP(Cable Modem) on FA23 from the CISCO 2950 SWITCH (24 Ports)

ROUTER (ON A STICK) on FA24 from the CISCO 2950 SWITCH

And the rest of the switch is FA1=VLAN 1; FA2=VLAN 2;FA10=VLAN 10

Our home network is connected to VLAN 10 with a IP Range of 192.168.10.x /24

After this power down , I was not able to look into the SWITCH via FA1 , the FIX IP in this switch was 192.168.1.251/24, the ONLY way to get access was via the consol port !!!

What a suprice when I connected my consol to the PC , I can see ROUTER_F342 , my router config is called ROUTER1841 and my switch config name is /was called SW24.

So it seems that after this Power Down , the router took or received a config from my provider ?!?

I have recovered the the file in the switch + the vlan.dat and now everithing works again.

How can I avoid that this switch receive again a wrong file , I have all the needed files on the products itself and I do not use a TFTP server.

I have atached some screen shot when my switch is starting up , and it seems that the switch receive a IP address from my ISP , I do not know why, in the config file I have given it a FIX IP 192.168.1.251/24 ?!?

So it seems that my ISP erase the config file and when the switch is empty ,the  swich look for :

tftp://255.255.255.255/router-confg

tftp://255.255.255.255/ciscortr.cfg

Etc ....

Until it find something.

I have tried after a complete recovery to switch off the power again for 10 minutes (ISP MODEM + SWITCH + ROUTER) and I was not able to reproduce the fault.

Can it be that due to this power failure in our area that some routers or switches send or broadcast this kind of things ?!?

PS: I will start my CCNA Training in Oktober , so sorry for the stupid quetions 

Thank You in advance for your help.

Best Regards,

Didier

[Alessio Andreoli · Accepted solution]

Hi Didier,

first of all Good Luck for your CCNA in October !! Then you understanding is correct. If you noticed, among the logs there is "autoinstall" enabled that is doing exactly what you have described. It is not a good idea to leave this feature on or to use it because every and each router is a separate story, but essentially it is using the tftp in the same way you described. Consider then that your modem is receiving the config from the ISP and it is very possible that a very similar mechanism is on for the modem too. it would e curious to see the config you had after the power down. Post it if you still have it.

thanks

Alessio

[Didier1966]

Hi Alessio,

Thank You for your prompt reply , unfortunatly I did not take a copy of what they send.

I will do wht you recomand , setting the AUTOINSTALL to disaple or off;

Thank You Again and Best Regards,

Didier

[Leo Laohoo · Accepted solution]

If you want to disable AutoInstall, disable VLAN 1.

Autoinstall requires VLAN 1 to be enable.  If it's disabled then there's no way for the switch to communicate using AutoInstall.

[Didier1966]

Thank You for this update , I was looking how to disable this , but you give me the solution

Best Regards,

Didier