Writing notes here for future reference. Connecting to serial console of the NMC, there is no password, and current firmware is:
Network Management Card Revision 6.1.17
Boot Code Linked Date: Jun 14 1995 at 15:24:25
Operation Code Linked Date: Apr 16 1999 at 14:29:08
Serial Number:B4F7VK1M
Main Menu
1 Configuration
2 Command
3 Feature Enable
Enter menu selection and press Return.
Menu Selection (1-3): old LAN IP was 192.77.203.193, I’ve changed it to 10.254.255.46. SNMP strings are default (public RO, private RW). RADIUS secret key: serialport
I saved config, then applied it by going to Command menu and resetting NMC. NMC is now pinging!