When working with Cisco 800 model routers (and probably any Cisco Integrated Services Router) you might run into an issue that the VLAN which is assigned to the LAN ethernet ports is in an “up/down” state.  This is because an SVI must meet all of the following conditions to transition to the full "up/up" state:

  • The VLAN must exist and be active in the VLAN database.
  • At least one switched port in the VLAN (access or trunk) must be up.
  • That port must be in the STP forwarding state.

Sometimes it is necessary to have that VLAN interface up even if there are no devices or ports using that VLAN.  [more]The most recent case that I experienced this need was when I was trying to transfer IOS images remotely across a VPN connection.  Because the transfer was traversing across the VPN I had to source the file transfer from the internal VLAN interface.   There weren’t any PC’s connected to the router so the VLAN interface was in an “up/down” state.  To resolve this issue, I could have either connected a PC or a loopback into the router or simply forced the VLAN into an “up/up” state.  Issuing the “no autostate” command on the VLAN interface will bring the interface up.  Basically, the command just tells the VLAN interface to ignore the above mentioned prerequisites.  Note: This command is only available in certain IOS images.