GATE CS 2007 Q67 — Fragmentation and IP Addressing, IPv4, CIDR

To find the maximum number of subnets and hosts, we analyze the structure of a Class B IP address:

• Class B Default Format: 16 bits for Network ID and 16 bits for Host ID.
• Subnet ID size: $6$ bits (borrowed from the Host ID part).
• Remaining Host ID size: $16 - 6 = 10$ bits.

Now, we calculate the maximum number of subnets and hosts per subnet based on traditional subnetting rules (RFC 950):

1. Maximum Number of Subnets:
   With $6$ subnet bits, we have $2^6 = 64$ possible combinations. Under the traditional standard (RFC 950), the subnet IDs consisting of all-zeros and all-ones are reserved (not used). $$\text{Maximum Subnets} = 2^6 - 2 = 64 - 2 = 62$$
2. Maximum Number of Hosts per Subnet:
   With $10$ host bits, we have $2^{10} = 1024$ possible combinations. The host IDs consisting of all-zeros (subnet address) and all-ones (directed broadcast address) are reserved. $$\text{Maximum Hosts per Subnet} = 2^{10} - 2 = 1024 - 2 = 1022$$

Therefore, the maximum number of subnets is 62 and the maximum number of hosts per subnet is 1022.