In IPv4 address size is of 32 bits so there are 2^ 32 hosts in the network.
In 1 sec----->500 packets by each host.
Therefore, in 1 sec,total number of packets present in the network is 500*(2^32).With 48 bits identication number, there are 2^48 packets possible.
So, 1 sec-------------> 500*(2^32) packets
? sec<------------- 2^48 packets
i.e. 131.07 sec