Well I'm not sure whether I'm missing something here. But all I've read is that if first octet of IP is within 0 – 127 then it is categorized as Class A subnet and correspondingly Subnet Mask for this is 255.0.0.0 but when I connect my system to Apple airport then my system gets IP as 10.0.1.4 however subnet mask is 255.255.255.0 not 255.0.0.0. Please explain what I'm missing here.
If there is something like for apple router subnet mask is calculated on some different flags then please let me know.
Best Answer
Classful addressing has been relegated to the dustbin of history, made obsolete by VLSM and CIDR. The only place it's still used today is Cisco certification exams.
What you're seeing here is VLSM (Variable Length Subnet Mask). VLSM has been the norm on the Internet since 1995 or so after having been proposed in 1985. So your reasoning is out of date by at least 17 years.
You're also confusing subnetworks with networks. Even with classful addressing, this would be a class A network. That would mean the network mask would be 255.0.0.0. But that wouldn't say what the subnet mask was. See this link for more details.