Intrvw
AMZN Networking
Round 1
- BGP Route manupulation
Directions?
- Anycast
- Linux check WSF
- SSL speed up at LB level:
Session Ticket OSPC Stapling
- Cookie Uses
- Google BBR - congestion control algorithm
- DNS check if reply is spoofed or not?
- How does DNS client knows when to switch to TCP?
TC Flag
Round 2
- Experience with diffcult customer
- Learnt from feedback
- Windows
- How to remotely access Windows server?
RDP, VNC (Teamviewer, Webex for PC) RDP Port no TCP port 3389 and UDP port 3389
- Page file
- Service
- Service fails, how to check logs? (Event logs viewer)
- Linux
- Kernel
- Inode
- Check CPU, Memory, HDD info?
- Check Load Average? What is the output?(1,5,15 min avrg), what does it mean?
- Check Clients we are connected to? netstat -ant -> Foreign Address
- ifconfig -a - eth0:1 - What does :1 mean? (vlan)
- Check file in use by which process? lsof
- Runlevels
- Check DNS config? /etc/resolv.conf & interface config
- Iptables?
- Networking
- NAT
- How does Traceroute works?
- Request & response headers
curl -v http://google.com
- Commands used in daily troubleshooting
telnet nc ipconfig netstat traceroute top ps free df dh
- Scenario
[PC]---------[Website] 1st attempt - 404 2nd attempt - 200 3rd attempt - 404 4th attempt - 200 LB having 2 servers, one is not having app installed, check logs & disable it.
Round 3 - Behavioral
Round 4 - Architecture
- Explain case you have worked - Voip CB Repro
- Design a Ecommerse website with full redundancy, explain protocols used:
- Avi SE scaling, use 3 node cluster for controller - Use 2 AZs - How DB will sync - GSLB usage - geodb Networking - how persistence will work - Storage redundancy - Storage slow, use SSD - Pics load slowly in Japan
Round 5 - Linux
- Boot process in detail
- What is kernel? How does it communicate with HW/User? System calls
- Name the various System calls
- What is initrd ? What it contains/does ? (drivers to load disk,etc)
- Runlevels
- Upstart/Systemd
- What is Swap?
- How to find swap usage?
- How to find if a file is moving from RAM to SWAP? iotop(process wise usage) & iostat(part wise usage)
- How to check processes using most CPU/How to check CPU usage per core?
- Process States:
- Stop (my answers) - Start - Running - Sleeping ==> Interupptable waiting/ uninterruptable waiting -> Explain each - Killed - Zombie
- Type of File systems - FAT32/ExFAT, NTFS, EXT3, EXT4
- How to use a brand new disk in Linux machine
- Format - Partition - Mount
- What are permissions -> 640?
6 -> user - Read/Write 4 -> group - Read 0 -> Others - None
- How to check Memory usage - top//free -m // cat /proc/meminfo
- Buffer/Cache field? - Swap field?
- How to troubleshoot if a file stopped coping in between saying no disk space, but disk space is there.
df -h => check free disk space df -i => Free inodes check
- What is inode? How can they get full(mail server; large no of empty files)?
Round 6 - Networking
- Design a website for 500 Employees - use 2 AZs?
- Troubleshoot a website not reachable?
curl -I, telnet, nc, ping
- How to check if DNS is working or not?
dig @42.2.2 google.com
- Check packet captures using tcpdump.
- Explain DNS resolution in Full details.
- Troubleshooting a slow website:
Top --> CPU, Memory, Process usages, Load avg df -h --> Disk usage free -m cat /proc/meminfo netstat -ant cpu ==> 0 "us" user space top -o %CPU
- Explain TCP Window? How it can be full
- OSPF vs BGP? why not use OSPF for Internet instead of BGP?
- OSPF packet types?
Hello DBD LSR LSU [LSAa] LSAck
- What is Area 0 in OSPF?
- BGP Attributes
- BGP getting more traffic from one ISP than other? How to balance that?
- What is DDOS attack? How to mitigate it?
Need to know about the type of attack Syn Flood attack can be mitigate by using Syn-Cookie
- What is Syn-Cookie used for?
Round 7
- Repro Attempt
- Something not done within committed time
- Something done differently from a colleague
- Something you have done apart from regular work
- Tough Feedback received; What you did about it.
AMZN DMS
- 1st Round Online Challenge
- Telephonic Round
Tell me something where you did something extra during a case/your job Tell me something where you learned something during a case/your job Where do you store your code(Github)? How can some one other edit code? How DNS works? Explain in detail. DNS traffic Flow? Search local cache > hosts file > DNS server What is VoIP? How SIP works? Scenario: [LB]------[srv1][srv2][srv3]srv4] Srv3 is slow, latency, how to troubleshoot? top, free -h, df -h How to check traffic requests coming per second? netstat -s, ss -s, tcpdump
Challenge
CouchBase
- OOM Killer
- Page Fault
A page fault (sometimes called #PF, PF or hard fault) is a type of exception raised by computer hardware when a running program accesses a memory page that is not currently mapped by the memory management unit (MMU) into the virtual address space of a process.
- Swap Memory
- DNS Rate Limiting Troubleshoot
Create Static entry Increase Cache Time
- DNS latency in Server or Network Troubleshoot:
Check RTT for other traffic & DNS Specific traffic.
- Print below logs:
startTime : 12332121324 endTime : 21342313222 serviceName : abc status : 200 ------------------------ startTime : 12332121324 endTime : 21342313222 serviceName : abc status : 200 ------------------------ startTime : 12332121324 endTime : 21342313222 serviceName : abc status : 200 ------------------------ startTime : 12332121324 endTime : 21342313222 serviceName : abc status : 200 ------------------------ startTime : 12332121324 endTime : 21342313222 serviceName : abc status : 200 ------------------------
- My Solution:
f=open('text.txt','r')
l=f.readlines()
a=[]
for i in l:
if ":" in i:
a.append((i.strip('\n')).split(':'))
b=[]
for i in range(len(a)):
b.append(a[i][0])
b=set(b)
for i in b:
print(i,end='')
for i in range(len(a)):
if "startTime " in a[i]:
print(a[i][1],a[i+1][1],a[i+2][1],a[i+3][1],end='')
print('\n', end="")
Juniper
Is UDP Stateful How is UDP connectionless FTP types What is Frag Offset IKE v1 vs IKE v2