September 2016

Cisco 871 Router: Quickly Change the ISP

Putty into the 871 Router

Run the command “Show Run” to start scrolling through and get the outside IP Interface, IP Address and Subnet Mask.

interface FastEthernet4
ip address %CurrentIPAddress% %CurrentIPSubnet%
!

Scroll further and get the IP Route (Gateway Address)

ip route 0.0.0.0 0.0.0.0 %CurrentGatewayIP%

Prpare a short script to remove the old ISP settings and add the new ISP settings.
Start with the Gateway (IP ROUTE).
Example below between the hypens.e

no ip route 0.0.0.0 0.0.0.0 %CurrentGatewayIP%
ip route 0.0.0.0 0.0.0.0 %NewGatewayIP%

interface FastEthernet4
no ip address %CurrentIPAddress% %CurrentIPSubnet%
ip address %NewIPAddress% %NewIpAddressSubnet%
!
Run the command “Conf T”

Copy and paste entire script into Putty.

Once internet is verified up and running, “Exit” out of Config mode.

Run the command “Write Mem“

XenServer: Rogue/Missing/Invisible Virtual Machine

Yesterday, I had the pleasure of finding out that there was an invisible/missing/rogue VM on one of the servers in our pool.

We had a “dead-beef” issue a few weeks prior and had attempted to migrate our VMs off to other members of the pool before rebooting the member. With that attempt, it caused all of the VMs to go into a paused state from which a forced shutdown was required. We rebooted the server at that point because it was the only way we could get the “dead-beef” issue recovered.

After the pool member reboot, the VMs would not start, so we cloned them and booted them up. Everything seemed fine in the next few weeks, until I decided to delete the originals as the replacements appeared to be functioning fine.

One of those servers had apparently been running in the background even though XenServer showed it as off.

We could ping it, see a MAC address for it that didn’t match the server it should have been, etc. Though, it didn’t show up in any VM list, be it from the XenCenter console, or through the “xe vm-list” command.

Later, we discovered that there was an extra domain (command: list_domains) on one of the servers. It’s possible that it could have been fixed by destroying that domain, but we ended up rebooting the entire pool. I started with that pool member after shutting down / migrating the existing VMs and placing it into Maintenance Mode.

The rogue server stopped responding pretty much immediately at this point and when it came back up it was no longer an issue.

TL;DR – Apparently, sometimes a server can be running in XenServer with nearly no record of it’s existence after being deleted in a “powered off” state.

Helping Out

I’ve spent a lot of time scouring the internet for solutions in my life. Sometimes I needed to piece multiple things together from multiple sources to get a decent fix. I have been documenting these things but I haven’t had a place to share them and I feel like other people could benefit from some simplified resources.

It’s my turn to give something back to the community that has helped me develop my career.