Interview Q&A / Computer Networks
Computer Networks interview questions
What happens when you open a website, TCP vs UDP, DNS and HTTP.
Prefer rapid revision? Practise Computer Networks short interview answers →
- How does DNS resolution work, step by step?
Your device asks a recursive resolver, which checks its cache and, if needed, asks a root server, then the TLD server (like .com), then the domain's authoritative server, which returns the IP address. Every answer carries a TTL, so resolvers and devices cache it and skip most of these steps next time.
IntermediateIn-depth4 min read - What is DNS TTL, and why do DNS changes seem to take time to "propagate"?
TTL is how many seconds resolvers may cache a record. When you change a record, resolvers that cached the old one keep serving it until its TTL expires, so different users see the change at different times.
BeginnerQuick answer1 min read - How does traceroute discover the path to a server?
It sends packets with TTL set to 1, then 2, then 3 and so on. Each router that drops a packet at TTL 0 replies with an ICMP Time Exceeded message, revealing its address, until the destination itself replies.
IntermediateQuick answer1 min read - What changes in a packet as it passes through routers?
The IP source and destination stay the same (without NAT), but each router decrements the TTL by 1 and the Ethernet frame is rebuilt with new source and destination MAC addresses for the next link.
IntermediateQuick answer1 min read