Multiple credentials same network

I wasn't able to find a way to do this. We have around 800 servers, many VLANs. Some servers, in the same VLAN, have different root passwords, different snmp strings, etc..  How can I have it scan the same network with different credentials?

I can't make a seconds scan and change the credentials, it's giving me an error when I try that.

Some are scattered in the same network so it makes it impossible to do in small sections.

Thanks