To verify in-band management is possible you need to check the running configuration (show running) and at least every switch should have an ip address assigned to the (virtual) interface vsan1, assuming the snmp and other settings are still correct.
An in-depth explanation of this can be found at this url:
I performed the following steps on each of our switches in our environment to have a back-end network in case of a LAN outage:
The way I've done this is create interfaces on VSAN1 on all of our switches
interface vsan 1
ip address 192.168.150.X
Then would create a default route for that network:
ip route 192.168.150.0 255.255.255.0 interface vsan 1
I'm not sure the above step was necessary because I then would turn on ip routing:
So as long as vsan 1 in the case is merged between the switches you need to get to you should be able to telnet from one switch to another at anytime. You can also use fabric manager and see the switches using this back-end network.
Just in case:
Should probably add that 192.168.150.0 network isn't being used anywhere else in our environment.