Final answer:
Four contiguous Class C networks can be aggregated into a /22 CIDR block if they align on a /22 boundary. The first Class C network's starting address must be a multiple of 4 in the last octet. An example is combining 192.168.4.0, 192.168.5.0, 192.168.6.0, and 192.168.7.0 into 192.168.4.0/22.
Step-by-step explanation:
Combining four Class C networks to create a /22 CIDR block would not pose a problem so long as the four Class C networks are contiguous and align on a /22 boundary. However, without specific network addresses, it is impossible to determine definitively. To form a /22 network, the starting address of the first Class C network must be a multiple of 4 in the last octet since a /22 includes 1024 addresses (or 4 Class C networks). If the networks are adjacent and align properly, they can be aggregated into a single /22 network.
Consider the following example: If the four Class C networks began with the addresses 192.168.4.0, 192.168.5.0, 192.168.6.0, and 192.168.7.0, they could be combined into a /22 network because they are consecutive and start from an address that is a multiple of 4. The resulting CIDR block would be 192.168.4.0/22, encompassing all four networks without any issues.