Hi From Seb:s example that we can use it but without reload. Do the tftp of the running config to the tftpserver. Edit the file, don't touch anything else but the example, vlan 3 interface g1/0/1  switchport trunk allowed vlan add 3 interface vlan 2  no ip address interface vlan 3  ip address 1.2.3.4 255.255.255.0  no shut   Now upload the file with tftp to the startup Now you can do this trick, configure the router, but not with conf term, instead use  configure mem then the router starts to configure using the startup config, and it reads the file from the start down to the end, executing every command int the startup, and if everything is as it was before all commands will just be the same, except for the changes You have done from the example. Beware of the fact that you have to have the "no ip address" on the old interface before adding th the address in the new interface. /Mikael   ... View more

Hi Reza has explained it well, just to try to explain further. It is still 2 physical boxes, however they are treated as if they where one box. So if you configure 1/0/1 as a routed interface with 192.168.1.1 as the example from Reza, and 2/0/1 with 192.168.2.1, you also configure the routes as Reza mentioned. Then if all is good both interfaces are alive and the route to 192.168.1.2 is then one in routingtable. If then switch one dies, then interface 1/0/1 is not available anymore so the routing will put in the the route to 192.168.2.2 instead. Then when switch one is back in business, and the 1/0/1 is up again, the original route will be inserted. /Mikael ... View more