At my old place of employment , we had 2 VLANs. We used secondary interfaces on a cisco 4000 router to do intervlan routing.
My question is, why didnt the network admins use subuinterfaces instead? Whats the pros and cons of secondary vs sub?
ps: 4000 router was running Cat 0S (is Cat0S an older Cisco operating system? Is IOS replacing it???)