LCA Network Configuration & Troubleshooting 3

Question 1

Which NetworkManager command-line tool is used to bring up a connection profile named 'office-vpn'?

Accepted Answer

nmcli con up office-vpn

Answer

'nmcli con up <name>' activates a connection profile managed by NetworkManager.

Question 2

What is the purpose of the /proc/sys/net/ipv4/ip_forward file?

Accepted Answer

It enables or disables kernel IP packet forwarding between interfaces

Answer

Writing '1' to ip_forward enables the Linux kernel to forward packets between network interfaces, making it act as a router.

Question 3

A user reports intermittent packet loss to a remote server. Which tool provides continuous per-hop latency and loss statistics in a single view?

Accepted Answer

mtr

Answer

'mtr' combines traceroute and ping, continuously updating per-hop packet loss and latency statistics.

Question 4

Which iptables chain is used to modify packets destined for the local machine before routing decisions are made?

Accepted Answer

PREROUTING

Answer

The PREROUTING chain (in the nat table) processes incoming packets before the routing decision, used for DNAT.

Question 5

You need to capture only TCP traffic on port 443 on interface eth0 using tcpdump. Which command is correct?

Accepted Answer

tcpdump -i eth0 tcp and port 443

Answer

tcpdump uses BPF filter syntax; 'tcp and port 443' captures only TCP packets on port 443.

(LCA) Certified Linux Administrator Practice Test