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Booting router without config


I'm pretty sure I already know the answer to this, but I wanted to ask some of you. Suppose you have a router die in the field in another state, country, etc. Cisco replaces that router, but it's going to have a blank config when your site receives it. How do you manage that router? We've thought about a tftp server onsite for the device to boot to, but in the end, I believe you're still going to have to touch the router to bring the ethernet interface up, configure for dhcp, and then configure the device to boot from the network instead of flash. Is there an easier way around it? We're trying to avoid having a user try to get into the device, plus we may not have a console cable onsite which would cause other issues.



HTH, John *** Please rate all useful posts ***

Booting router without config


We put out-of-band devices at remote locations. They are well worth their cost. We used Avocents and put the modem cards in them. We could access any device via their console and if the entire site was down we could dial in to the Avocent and still get console access for troublshooting. You can do the same thing with Cisco routers and async cards.

Hall of Fame Super Blue

Booting router without config

Well Cisco routers and switches support the archaic version of ZeroTouch SmartInstall. 

If you take a router without a config and plug it into your network, you will notice that as soon as the router gets an IP address it goes out and look for a specific file.  I forgot what that file is but that was originally how we did our router rollout.  We have a "flat" config file and it populates everything but the IP address.  So once we take the router off field we just enable DHCP.  Contact the router and change the IP address to static and it's good. 

Booting router without config

Hi John,

I used to work for a large ISP. They used the method that Leo was describing. The router if NVRAM is empty will try to find a configuration file named so if the router has a hostname of r1 it will look for r1-cnfg. The first step is to acquire IP address via DHCP. So there needs to be an ip helper configured to reach the DHCP server. Also there should ba a reverse DNS mapping so that the router can find its hostname by looking at the IP. It then knows which configuration to get which is stored on a TFTP server.

This method worked well and scaled nicely. Once the information is in DHCP, DNS and TFTP, staging and replacing equipment is easy.

I'm not sure if there are more modern methods but this should at least give you an idea what is possible. Here are some links describing the process:

Daniel Dib
CCIE #37149

Please rate helpful posts.

Daniel Dib CCIE #37149 Please rate helpful posts.

Booting router without config

Thanks everyone! I'm looking to lab this up at the beginning of the year, and these are helpful suggestions.


HTH, John *** Please rate all useful posts ***
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