250 Network Administrator Interview questions and answers

The 250 Network administrator Interview Questions & Answers Ebook contains 250 questions based on networking concepts like Firewall, NAT, VPN, Wireless networking, TCP/IP, Frame relay, Routing and switching. The book also includes scenario based questions with diagrams and detailed tutorials. It is ideal for candidates aspiring for networking job interview.

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Sample questions

Question 1

What happens when a TCP based packet exits a NAT firewall

When a TCP packet exits a NAT firewall, the source port and destination port number in the TCP header along with the source and destination IP address in the IP header is added to the Network address translation table. After this operation is performed, the source IP address in the IP header is re-written with the IP address of the NAT firewall following which the packet exits the firewall.

Question 2

What happens when a TCP based packet returns to a NAT firewall

When a TCP packet which exited the NAT firewall returns, the firewall looks into the destination port in the TCP header. It would then identify the appropriate entry in the NAT table which has the corresponding entry. After the packet is identified, the destination IP address in the IP packet which now contains the IP address of the NAT firewall would be re-written with the actual initiators IP address, following which the packet is sent to the intended recipient.

Question 3

Explain a practical scenario why split tunneling is used

Assume a scenario where a user initiates a VPN tunnel using a remote access client. Once the connection is established, all packets would be sent through the VPN tunnel which is created. This would also apply for internet bound packets. Internet bound packets should not be sent through the VPN tunnel. To avoid internet packets to be sent through the tunnel, split tunneling feature is used. When the feature is enabled, all internet packets would be sent through the adapter which is associated with the internet connection on the client and not through the VPN tunnel.

Question 4

What is the difference between TCP 4 way handshake and WPA 4 way handshake

TCP 4 way handshake is used for tearing down a TCP session between a client and a server. WPA 4 way handshake is used by wifi clients and access points configured with WPA to derive session‟s keys for encryption and authentication.

Question 5

Which protocol would you block on a firewall for blocking tracert

Tracert uses ICMP at the network layer. ICMP should be denied on a firewall to block tracert.

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