Hi Mahesh
backup-router 192.168.253.254 is the gateway to reach private management network.
And destination denotes the subnet of management network.
Backup-router IP would be in the same subnet as that of your fxp0 IP.
If fxp0 IPs of two nodes are of different subnet and connected to different switch/L3 device, then you can have different backup-router ip.
In myexperience, typical deployment would be to have single management network and fxp0s of both nodes connected to same switch(in this scenario your backup-router and destination would be the same).
Regards,
Raveen