I am really hoping that someone can help me, if not, then no worries, if yes, I am grateful!
We had a power outage and the router which is 2811 running VM is no longer showing all of the configuration and it has a different hostname and doesn't accept any of the sh commands, the sh run only shows default conf but everything works just fine.I was trying to save the config and transfer them to a different server.
To add to what Mohammed said, issue the command "show version" and look at the configuration register. It should be 0x2102. If it is another value (such as 0x2101) that may be the cause of your issue.
Also, issue the command "show startup-config". This will tell you if the original configuration is still on the router.
What is the current hostname? Is it "rommon 1" or something similar? If so, issue the following command to change the config register back to 0x2102:
rommon 1 >confreg 0x2102
Then reboot or power-cycle the router.
Let us know how it goes.
Is this startup-config the same or not the same as your current running-config?
If it is the same as your current running-config, then it seems your former running-config was not saved prior to the power outage. If that is the case, your old config is lost and you'll have to recreate it.
If the current startup-config is not the same as your current running-config, you can place the startup config into your running-config with the command copy startup-config running-config
Also, if the current startup-config is not the same as the current running-config, then there may be a serious problem with your router as the config-reg of 0x2102 should have caused the startup-config to be loaded into the running-config at boot. As this did not happen, it could be an anomaly but it could also indicate an issue. If this is the case, I would suggest performing a reload and see if the startup-config is loaded into the running-config. If it does not, you will want to contact TAC.