Tip for home lab builders

Make sure you check the configuration register value whenever a router is purchased.

I never thought to look at it because I never save my configurations (and assumed the resellers would wipe any configurations). Tonight, I was looking at IOS and memory for my routers and noticed one was set to 0x2142. Hmmmm.... let's change that back to 0x2102.

Hilarity ensued upon reload.

I ended up having to get into the router via rommon to change it back to 0x2142 so I could erase the startup-config.

Hope this helps someone down the line.

If this isn't posted in the right forum, please move it to where it's most appropriate.

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Comments

okplaya

This seems to be the "standard" when buying used kit off ebay. I'm not sure why however. Having it set to 0x2142 just says "ignore startup config when I boot". I received a router with a startup configuration and they had cool passwords like app1e$auce. When we RMA our legacy stuff we wipe them, but I guess other companies don't bother. These resellers must get them, get into rommon, and just change the config-register to 0x2142 and sell. Strange.

On another note, this is actually good experience because you're less likely to experience this on a simulator/emulator.

Good Tip!

j-man

The router in question was so locked down that only the console was available but only by password. All interfaces were shut down.

I've bought 4 routers from ebay and this was the only one that was set like this. Apparently the reseller set it that way so it would boot normally. They didn't bother to clear the startup-config.

All I'm saying is that always make sure you check the config register whenever something is bought off ebay.

alan2308

Back when I bought my first router and didn't have any idea what a config register was, I just assumed there was something wrong with the router and had to save my configuration on my desktop. DOH!

Every piece of gear that I bought had the config still on it. Some sellers changed the config register to 0x2142, some just sold it as it. One reseller actually wiped the configs, but left the backups (config.old). I learned a lot about the network of a bank's headquarters from those two switches as the config had real good comments.

geek4god

j-man wrote: »

Make sure you check the configuration register value whenever a router is purchased.

I never thought to look at it because I never save my configurations (and assumed the resellers would wipe any configurations). Tonight, I was looking at IOS and memory for my routers and noticed one was set to 0x2142. Hmmmm.... let's change that back to 0x2102.

Hilarity ensued upon reload.

I ended up having to get into the router via rommon to change it back to 0x2142 so I could erase the startup-config.

Hope this helps someone down the line.

If this isn't posted in the right forum, please move it to where it's most appropriate.

So any tips on restoring one to factory defaults?

okplaya

geek4god wrote: »

So any tips on restoring one to factory defaults?

If the device doesn't have a startup-configuration to load then it will essentially be back to factory default.

What's the issue with your device?

jdfriesen

geek4god wrote: »

So any tips on restoring one to factory defaults?

router>enable
router#configure terminal
router(config)#config-register 0x2102
router(config)#end
router#write erase

j-man

geek4god wrote: »

So any tips on restoring one to factory defaults?

Because I was completely locked out of the router after I changed the configuration register to 0x2102, I needed to first get the router to boot into ROMMON so I could reset that value back to 0x2142.

To do so I followed steps 1 - 6 found here: Password Recovery Procedure for the Cisco 2600 and 2800 Series Routers - Cisco Systems

That allowed me to do what jdfriesen said above.

Worked like a charm.

WillTech105

This was actually a great learning exp for me -- I bought several firewalls and routers off ebay with them being in the wrong registar -- granted I was sitting there for a hour or two learning, googling, and playing but it gives you alot of confidence in the field when you find it in the real world.

j-man

WillTech105 wrote: »

This was actually a great learning exp for me -- I bought several firewalls and routers off ebay with them being in the wrong registar -- granted I was sitting there for a hour or two learning, googling, and playing but it gives you alot of confidence in the field when you find it in the real world.

simulpost!

Yeah. I was having a hard time remembering which configuration register values did what but after the other day, I've got them down.

I've said it once and I'll say it again, there is nothing like having your hands on the real thing.

mikej412

Password Recovery was a lab when I did the CCNA Network Academy -- and the configuration register values were fair game for the CCNA exam.

Here's the starting point to find the password recovery method for almost anything Cisco (good for the home lab and when you're on the job): Password Recovery Procedures - Cisco Systems

earweed

Good tips here. I haven't had these issues (yet) but decided last night to see what the issue was so I created it and did a fix. Good practice. Maybe I'll be getting back into feeling like studying my CCNA stuff again soon.