Initial round was 1 hr test conducted at hackerrank, which consists of 2 coding questions and around 20 MCQ.
- Length of longest Subsequence with unique characters.
Apart from this complex input-output questions(based on pointers), questions on probability, clocks, N/w questions.
After first round they shortlisted 21 people out of 326.Second round was technical + HR in this round i was initially asked about Different layers of TCP/IP model along with protocols which runs on them, difference between router and switch, then he asked me difference between process and thread with example, concept of paging, some really good questions on pointers, code to print nth node from end of linked list, Memory layout of C program, semaphore & mutex difference, Flip nth bit of given number, concept of VLAN, Some basics HR questions like why CISCO, weakness, strengths etc .Two puzzle problem
Round 3: Interviewer started with my project and we had a long discussion on my project (make sure you have in-depth knowledge of your project) then he asked me about DHCP, DNS (he got really deep into these concepts to check basic understanding).He asked me to design a DS based on some given condition, I suggested the use of Linked List with some modification. He asked me some output based questions based on pointers(really tricky), basic questions on bit manipulation, the difference between a recursive function calling itself vs function with an infinite while loop, difference between private and protected.
Tips:CISCO mainly focuses on how good you are at the basics of OS, CN, C, OOPS, DS.They focus a lot on pointers and bit manipulation so read them well.