LPIC-2 Network Client Management — Timed 50 Questions

Question 1

A system administrator needs to configure a Linux client to use a specific DNS server for a particular domain. Which file should be modified to achieve this?

Accepted Answer

Edit /etc/resolv.conf. The /etc/resolv.conf file is the primary configuration file for DNS resolution on Linux systems. It allows specifying DNS servers (nameserver entries) and search domains, and can be configured to use a specific DNS server for a particular domain by adding a 'domain' or 'search' directive along with the appropriate nameserver. This file is read by the resolver library (glibc) during DNS lookups.

Answer

Edit /etc/hosts

Answer

Edit /etc/networks

Answer

Edit /etc/nsswitch.conf

Question 2

A Linux client is unable to resolve hostnames for external domains but can ping internal hosts by IP. The /etc/resolv.conf file is correctly configured with a valid DNS server. What is the most likely cause?

Accepted Answer

The search domain in /etc/resolv.conf is incorrect, causing the resolver to append an inappropriate domain to queries.. When a search domain is incorrectly configured in /etc/resolv.conf, the resolver appends that domain to single-label hostnames before querying the DNS server. For external fully qualified domain names (FQDNs), this can cause the resolver to send queries like 'externaldomain.com.incorrect.domain' instead of the intended domain, leading to resolution failures. Since internal IPs are reachable (bypassing DNS) and the DNS server itself is valid, the issue is most likely the resolver's domain search behavior.

Answer

The /etc/hosts file contains an entry that overrides the DNS resolution for external domains.

Answer

The nmblookup service is not running.

Answer

The /etc/nsswitch.conf file is missing the 'dns' service in the 'hosts' line.

Question 3

A Linux client is experiencing slow name resolution. The /etc/nsswitch.conf file has the line 'hosts: files dns'. The /etc/hosts file contains many entries. What is the most effective way to improve resolution speed?

Accepted Answer

Change the nsswitch.conf line to 'hosts: dns files'. The current order 'hosts: files dns' causes the resolver to check the entire /etc/hosts file first for every query, which is slow when the file contains many entries. Reversing the order to 'hosts: dns files' makes the resolver query DNS first, which is typically faster for most lookups, and only falls back to the local file if DNS fails. This directly addresses the bottleneck without requiring additional services or data removal.

Answer

Increase the DNS timeout in /etc/resolv.conf

Answer

Install and configure nscd (Name Service Cache Daemon)

Answer

Remove all entries from /etc/hosts except localhost

Question 4

An administrator wants to ensure that a Linux client sends all DNS queries to a specific DNS server without relying on DHCP-provided DNS servers. Which configuration files should be modified?

Accepted Answer

Edit /etc/dhcp/dhclient.conf to add 'supersede domain-name-servers <desired IP>;'. The dhclient.conf file allows an administrator to override DHCP-provided DNS servers using the 'supersede' directive. This forces the DHCP client to ignore the DNS servers received from the DHCP server and instead use the manually specified DNS server when writing /etc/resolv.conf. This is a standard method for controlling DNS resolution on systems using dhclient.

Answer

Configure NetworkManager to ignore DNS from DHCP and set the DNS manually in the connection profile

Answer

Edit /etc/sysconfig/network-scripts/ifcfg-eth0 and set PEERDNS=no and DNS1=<desired IP>

Answer

Edit /etc/resolv.conf and set the nameserver to the desired IP

Question 5

Which TWO commands can be used to display the current DNS resolver configuration on a Linux system? (Select TWO.)

Accepted Answer

nmcli dev show. Option B (nmcli dev show) is correct because NetworkManager's nmcli tool displays per-device IP configuration, including the DNS servers currently in use (the IP4.DNS/IP6.DNS fields), reflecting the active resolver configuration. Option C (resolvectl status) is correct because it queries systemd-resolved and shows the current DNS servers, DNS domains, and per-link resolver settings actually in effect. Option A (dig localhost) only performs a DNS query for the name 'localhost' and does not report resolver configuration. Option D (nslookup) without arguments enters interactive mode or queries a name, but it does not display the system's configured DNS servers. Option E (cat /etc/resolv.conf) is not marked correct here because on modern systems it is often a stub or symlink managed by systemd-resolved/NetworkManager and may not reflect the true active resolver configuration.

Answer

dig localhost

Answer

nslookup

Answer

cat /etc/resolv.conf

Question 6

Which THREE conditions can cause a Linux DHCP client to fail to obtain an IP address? (Select THREE.)

Accepted Answer

A firewall on the client is blocking UDP port 67 (DHCP server).. Option A is correct because a DHCP client sends its initial DHCPDISCOVER from source UDP port 68 to destination UDP port 67, so a local firewall blocking UDP 67 prevents the client from reaching the DHCP server and obtaining a lease. Option C is correct because when the DHCP server's address pool is exhausted, it has no free leases to offer, so the client's DHCPDISCOVER goes unanswered and it falls back to an APIPA address (169.254.0.0/16). Option D is correct because if the DHCP server uses MAC address filtering and the client's MAC is not on the allow list, the server silently discards the request, so no lease is offered. Option B is not correct because DHCP servers are commonly configured with a scope matching the client's subnet, and a mismatched subnet alone does not inherently prevent a lease if the server is reachable via a relay; the real issue would be reachability, not the subnet value itself. Option E is not correct because a statically configured interface simply does not run the DHCP client, so it is not a failure to obtain an address via DHCP.

Answer

The DHCP server is configured with a different subnet than the client's broadcast domain.

Answer

The client interface is configured with a static IP address.

Question 7

Refer to the exhibit. The output shows a DHCP exchange between a client (MAC 00:1a:2b:3c:4d:5e) and a server (192.168.1.1). The client is not obtaining an IP address. What is the most likely reason?

Accepted Answer

The client's /etc/dhcp/dhclient.conf contains a 'reject' statement that rejects offers from this server.. The DHCP client can be configured with a 'reject' statement in /etc/dhcp/dhclient.conf to ignore offers from specific servers. In this scenario, the client sends a DHCPDISCOVER, receives a DHCPOFFER from 192.168.1.1, but then does not proceed to DHCPREQUEST, indicating the offer was rejected locally. This matches the behavior of a reject rule, which causes the client to discard the offer without further communication.

Answer

The DHCP server did not receive the client's request.

Answer

The DHCP server is not reachable from the client.

Answer

The client's MAC address is not authorized on the DHCP server.

Question 8

Refer to the exhibit. A user on the client tries to ping 'server1' and gets an unknown host error. What is the most likely cause?

Accepted Answer

The DNS server has no record for 'server1.example.com'.. The error 'unknown host' indicates that the client's DNS resolution failed for the hostname 'server1'. Since the client likely uses a fully qualified domain name (FQDN) lookup or appends a search domain, the most common cause is that the DNS server does not have an A or AAAA record for 'server1.example.com'. Without a matching record, the resolver returns NXDOMAIN, leading to the 'unknown host' error.

Answer

The search domain is missing.

Answer

The DNS server IP is incorrect.

Answer

Only one nameserver is specified, causing a timeout.

Question 9

A system administrator notices that a Linux client is unable to resolve hostnames after connecting to a new network. The client uses DHCP and the /etc/resolv.conf file contains only the loopback address 127.0.0.1. Which of the following is the most likely cause?

Accepted Answer

The client is configured to use a local DNS resolver such as systemd-resolved or dnsmasq.. When /etc/resolv.conf contains only 127.0.0.1, it typically indicates that a local DNS resolver (like systemd-resolved or dnsmasq) is running on the client. These resolvers bind to the loopback address and handle DNS queries locally, often forwarding them to upstream servers provided by DHCP. The client can still resolve hostnames if the local resolver is properly configured to use the DHCP-supplied DNS servers, so the presence of 127.0.0.1 alone does not imply a failure.

Answer

The DHCP server did not provide DNS server information.

Answer

The /etc/resolv.conf file is a symbolic link to /run/NetworkManager/resolv.conf.

Answer

The /etc/resolv.conf file is not being updated by the DHCP client.

Question 10

A Linux workstation must be configured to automatically mount an NFS share from server nfs.example.com:/exports/data at boot time. The share should be mounted with noexec and nosuid options. Which line should be added to /etc/fstab?

Accepted Answer

nfs.example.com:/exports/data /mnt/data nfs noexec,nosuid,_netdev 0 0. It specifies the NFS filesystem type, includes the required mount options (noexec, nosuid, _netdev), and uses the correct fstab format. The _netdev option is critical for network filesystems to ensure the system waits for network availability before attempting the mount at boot time.

Answer

nfs.example.com:/exports/data /mnt/data nfs noexec,nosuid 0 0

Answer

nfs.example.com:/exports/data /mnt/data auto noexec,nosuid,_netdev 0 0

Answer

nfs.example.com:/exports/data /mnt/data nfs4 noexec,nosuid 0 0

Question 11

You are troubleshooting a Linux client that is unable to connect to the internet. The client is configured to use DHCP on interface eth0. The output of 'ip addr show eth0' shows that the interface has an IP address 192.168.1.100/24, but there is no default gateway. The output of 'ip route show' shows only the local subnet route. The DHCP server is at 192.168.1.1 and is functioning correctly. You have verified that the DHCP client (dhclient) is running, and the lease file /var/lib/dhclient/dhclient-eth0.leases exists and contains option routers 192.168.1.1. Which of the following commands should you run to resolve the issue?

Accepted Answer

dhclient -r eth0 && dhclient eth0. The DHCP client has already obtained a lease with the correct gateway (192.168.1.1), but the default route was not applied. Running `dhclient -r eth0` releases the current lease, and `dhclient eth0` renews it, forcing the client to re-apply all options from the lease, including the default gateway route. This is the standard way to reinitialize the interface's network configuration from the DHCP server without restarting the entire networking service.

Answer

systemctl restart networking

Answer

ip route del default

Answer

ip route add default via 192.168.1.1

Question 12

Which TWO tools can be used to configure network interfaces on a Linux system?

Accepted Answer

nmcli. nmcli (A) is correct because it is the command-line front end for NetworkManager and can create, modify, activate, and deactivate network connections, including IP addressing and interface state. ip (C) is correct because the iproute2 suite's ip command configures interfaces directly, e.g., 'ip addr add' and 'ip link set', replacing legacy tools. route (B) only manipulates the kernel routing table, not interface configuration. ifconfig (D) is a legacy net-tools utility that can display and set interface parameters, but it is deprecated and not one of the two intended answers here. netstat (E) only reports network connections, routing tables, and interface statistics; it does not configure interfaces.

Answer

route

Answer

ifconfig

Answer

netstat

Question 13

Based on the exhibit, which command would change the DNS server to 1.1.1.1 for the connection MyConnection?

Accepted Answer

nmcli con mod MyConnection ipv4.dns 1.1.1.1. The `nmcli con mod` command modifies an existing connection profile, and the `ipv4.dns` property sets the DNS server for IPv4. The property name is case-sensitive and must be lowercase `ipv4.dns` as per NetworkManager's D-Bus API. This command replaces any existing DNS servers with the specified value.

Answer

nmcli con mod MyConnection IP4.DNS 1.1.1.1

Answer

nmcli dev mod eth0 ipv4.dns 1.1.1.1

Answer

nmcli con mod MyConnection +ipv4.dns 1.1.1.1

Question 14

You are a system administrator at a small company. The network uses DHCP to assign IP addresses to clients. Recently, some users reported intermittent network connectivity issues. Upon investigation, you notice that the DHCP server is running on a Linux server with the ISC DHCP daemon. The server log shows many 'DHCPREQUEST' messages from a particular MAC address with frequent changes in requested IP addresses. Users with that MAC address are experiencing IP address conflicts and connectivity drops. What is the most likely cause and the best corrective action?

Accepted Answer

Identify the device with that MAC address and replace its network interface card.. The frequent DHCPREQUEST messages from the same MAC address requesting different IP addresses indicate a faulty network interface card (NIC) that is generating random or corrupted DHCP requests, likely due to hardware malfunction. Replacing the NIC eliminates the root cause by stopping the spurious traffic, whereas other options only mask symptoms or fail to address the hardware fault.

Answer

Increase the DHCP lease time to reduce the frequency of renewals.

Answer

Add a static DHCP mapping for the problematic MAC address to a reserved IP.

Answer

Restart the DHCP daemon to clear the lease database.

Question 15

Match each NFS version to its feature.

Accepted Answer

NFSv2: Stateless protocol using UDP, limited to 32-bit file handles. NFS versions evolved from stateless NFSv2 (UDP, 32-bit) to NFSv3 (TCP, 64-bit, async writes) to stateful NFSv4 (compound RPC, security, delegation). Common confusions include attributing v4 features to v2 and v2 limitations to v3.

Answer

NFSv2: Introduced compound RPC and stateful operations

Answer

NFSv3: Limited to UDP and 32-bit file handles

Question 16

An administrator configures LDAP authentication on a Linux client. After making changes to /etc/nsswitch.conf and /etc/pam.d/system-auth, users can log in but cannot execute commands like 'id username'. What is the most likely cause?

Accepted Answer

nsswitch.conf lacks 'ldap' for passwd. The 'id username' command relies on the Name Service Switch (NSS) to resolve user and group information from configured sources. If 'ldap' is not listed for the 'passwd' database in /etc/nsswitch.conf, the system will not query the LDAP server for user account details, even though PAM may have been configured to authenticate against LDAP. This mismatch allows login (via PAM) but prevents user attribute lookups (via NSS).

Answer

LDAP server is not reachable

Answer

LDAP binddn is missing

Answer

PAM configuration is incorrect

Question 17

A Linux server exports a directory /data via NFS to a client. The client mounts it with 'mount -t nfs server:/data /mnt/data'. Write operations from the client fail with 'Permission denied' on some files. The server's /etc/exports contains: /data 192.168.1.0/24(rw,root_squash). What is the most likely issue?

Accepted Answer

root_squash maps root to nobody. The 'root_squash' option in /etc/exports maps the UID 0 (root) on the client to the 'nobody' user (typically UID 65534) on the server. When a client user with UID 0 attempts to write to files owned by other users or with restrictive permissions, the server sees the request as coming from 'nobody', which lacks write access, resulting in 'Permission denied'. This is the most likely cause because the client mount command does not specify 'no_root_squash', and the server's export explicitly enables root squashing.

Answer

NFS version mismatch

Answer

Client mount option 'noexec'

Answer

Missing 'rw' option in /etc/exports

Question 18

A Samba share is configured with 'valid users = @staff' but users in the staff group still get 'NT_STATUS_ACCESS_DENIED' when accessing the share. The server uses 'security = user'. Which additional configuration is required?

Accepted Answer

Run smbpasswd -a for each user. With 'security = user', Samba requires each user to have a separate Samba password stored in the smbpasswd file (or another passdb backend). Even if a user is a member of the 'staff' group and exists in the system's /etc/passwd, they cannot authenticate to the share without an smbpasswd entry. Running 'smbpasswd -a' for each user creates that entry, resolving the NT_STATUS_ACCESS_DENIED error.

Answer

Set 'guest ok = yes'

Answer

Set 'force group = staff'

Answer

Add the share to [global]

Question 19

A company uses NIS for user authentication. A client cannot log in with network accounts but local accounts work. Which command should be used to check if the client is bound to the NIS domain?

Accepted Answer

ypwhich. The `ypwhich` command is used to display the NIS server to which the client is currently bound. If the client is not bound to any NIS domain, `ypwhich` returns an error, confirming the binding issue. This directly checks the NIS client-server binding, which is essential for network authentication.

Answer

ypset

Answer

ypcat passwd

Answer

domainname

Question 20

To ensure LDAP communication is encrypted, an administrator configures LDAP over SSL (LDAPS) on port 636. Which configuration file on the client should be modified to specify the LDAP server with TLS?

Accepted Answer

/etc/ldap/ldap.conf. The LDAP client configuration file on Linux systems is typically located at /etc/ldap/ldap.conf (or /etc/openldap/ldap.conf on some distributions). This file is used by LDAP client libraries (e.g., libldap) to specify the LDAP server URI, including the use of TLS/SSL via the ldaps:// scheme or the TLS_REQCERT directive. Modifying this file allows the client to connect to an LDAP server over port 636 with encryption.

Answer

/etc/pam_ldap.conf

Answer

/etc/openldap/ldap.conf

Answer

/etc/nsswitch.conf