Hello Sairam,
please find your answers inline:
Q1. Can the connectivity between Primary and failover be L3 network?
Fayyaz: Yes, depending upon your WAN link bandwidth, Failover will fetch the backup of the primary server, so faster the link the better.
Q2. What is the bandwidth required between these two Airwaves?(2000APs will be discovered from day1)
Fayyaz: It depends upon the historical data retention on your primary server, keep the settings to default retention settings and we do not have any set limit for the WAN uplink, faster the better. coz, in the event of failover, Failover will take the current backup of the primary via scp, and work as primary.
hope this helps..
--