LPIC-2 Practice Test 22 — 15 Questions

Question 1

A system administrator recently configured two NICs in a bonding interface (bond0) using mode 1 (active-backup). Although both links appear up, traffic never fails over when the primary link goes down. Which command should the administrator use to diagnose the bonding status and determine the root cause?

Accepted Answer

cat /proc/net/bonding/bond0. Option B is correct because /proc/net/bonding/bond0 is the kernel-level interface that exposes the current bonding driver state, including active slave, link status, and failover counters. In mode 1 (active-backup), this file shows whether the primary interface is actually marked as 'up' by the bonding driver and whether the backup interface is ready to take over. The administrator can check for issues such as the primary link being stuck in a 'down' state due to misconfigured MII monitoring or missing 'miimon' parameter.

Answer

netstat -i

Answer

ifconfig bond0

Answer

ethtool bond0

Question 2

A Linux server requires several VLAN interfaces on eth0. The network switch expects 802.1Q tagged frames for VLAN 10. Which command correctly creates the VLAN interface?

Accepted Answer

ip link add link eth0 name eth0.10 type vlan id 10. Option C is correct because the `ip link` command with the `type vlan id 10` parameter creates a VLAN subinterface on eth0 that tags outgoing frames with VLAN 10 using the 802.1Q standard. This is the modern, recommended method for VLAN interface creation on Linux, replacing legacy tools like `vconfig`.

Answer

modprobe 8021q; ifconfig eth0 up

Answer

vconfig add eth0 10

Answer

ifconfig eth0:10 192.168.10.1/24 up

Question 3

Which TWO tools are commonly used for traffic shaping and QoS on Linux? (Choose two.)

Accepted Answer

wondershaper. Wondershaper is a user-friendly shell script that wraps the `tc` command to simplify traffic shaping by limiting bandwidth on a network interface. It uses the Linux kernel's QoS capabilities, specifically the HTB (Hierarchical Token Bucket) queuing discipline, to prioritize and throttle traffic. This makes it a common tool for basic traffic shaping tasks on Linux.

Answer

ethtool

Answer

iptables

Answer

route

Question 4

Your company has a Linux server acting as a router with three VLAN interfaces: eth0.10 (192.168.10.1/24), eth0.20 (192.168.20.1/24), and eth0.30 (192.168.30.1/24). The server has a default route via eth0 (native VLAN) to the internet gateway at 10.0.0.1. Internal hosts can communicate between VLANs, but cannot reach the internet. You have verified that the default route is present and that the gateway is reachable from the router itself. The iptables FORWARD chain policy is ACCEPT, and no filtering rules are defined. However, you notice that ip_forward is enabled. What is the most likely missing configuration?

Accepted Answer

Add iptables MASQUERADE rule on the outgoing interface (eth0).. The router itself can reach the internet, but internal hosts cannot because traffic from the internal VLANs (192.168.10.0/24, 192.168.20.0/24, 192.168.30.0/24) that is forwarded to the internet via eth0 (10.0.0.0/?) has a source IP from the private RFC 1918 address space. The internet gateway (10.0.0.1) will not route packets back to these private addresses, and even if it did, the return packets would not be delivered to the originating internal host without source NAT. Adding an iptables MASQUERADE rule on the outgoing interface (eth0) performs source NAT (SNAT), rewriting the source IP of forwarded packets to the router's own IP on eth0, so that the internet gateway sees return traffic destined to the router, which then de-masquerades and forwards it back to the correct internal host.

Answer

Enable net.ipv4.ip_forward in sysctl.conf.

Answer

Add a static route on the internal hosts to the internet gateway.

Answer

Disable firewalld to ensure no packet filtering.

Question 5

A company's Linux router uses iptables. The administrator needs to log all dropped packets (by default policy) before they are dropped. Where should the LOG rule be placed?

Accepted Answer

In the FORWARD chain with -j LOG --log-prefix 'DROPPED' and then -j DROP. Option D is correct because the LOG rule must be placed in the FORWARD chain before the DROP action to log packets that are dropped by the default policy. In iptables, the LOG target does not terminate the rule; it logs the packet and then continues to the next rule. By placing `-j LOG --log-prefix 'DROPPED'` followed by `-j DROP`, the packet is logged before being explicitly dropped, ensuring that packets matching the default policy (which drops at the end of the chain) are captured in the log. The FORWARD chain is the correct chain for a router handling traffic that is not destined for the router itself.

Answer

In the FORWARD chain with target LOG

Answer

In the INPUT chain before the drop rule

Answer

In a custom chain called LOGDROP and jump to it

Question 6

Which of the following is the correct command to add an IPv6 address 2001:db8::1/64 to interface eth0?

Accepted Answer

ip -6 addr add 2001:db8::1/64 dev eth0. Option A is correct because the `ip -6 addr add` command is the proper way to add an IPv6 address to an interface using the `ip` tool from the iproute2 suite. The `-6` option restricts the operation to IPv6, and the address must include the prefix length (`/64`) to define the subnet. The `dev eth0` parameter specifies the target interface.

Answer

ip addr add 2001:db8::1/64 dev eth0

Answer

ip -6 addr add 2001:db8::1 dev eth0

Answer

ip link set eth0 ipv6 2001:db8::1/64

Answer

ifconfig eth0 inet6 add 2001:db8::1/64

Question 7

An administrator is troubleshooting IPv6 connectivity on an interface with link-local address fe80::1. Which command correctly pings that address from the local host, ensuring the packet uses the correct interface?

Accepted Answer

ping6 -I eth0 fe80::1. Option D is correct because the `ping6 -I eth0 fe80::1` command explicitly binds the ICMPv6 echo request to interface `eth0`, which is required when pinging a link-local address (fe80::/10). Link-local addresses are not globally unique; they are scoped to a specific network segment, so the kernel must know which interface to send the packet out of. Without the `-I` option, the system may fail to route the packet or send it out the wrong interface.

Answer

traceroute6 -i eth0 fe80::1

Answer

ping6 fe80::1

Answer

ping -6 eth0 fe80::1

Question 8

A Linux router running FRR (Free Range Routing) needs to participate in OSPF with adjacent Cisco routers. Which configuration file should be modified to enable OSPF?

Accepted Answer

/etc/frr/frr.conf. FRR (Free Range Routing) stores its unified routing protocol configuration in /etc/frr/frr.conf. This file is the primary configuration file for all FRR daemons, including OSPF, and is read by the frr service at startup. Modifying this file and then reloading FRR enables OSPF on the Linux router to peer with adjacent Cisco routers.

Answer

/etc/quagga/ospfd.conf

Answer

/etc/network/interfaces

Answer

/etc/ospfd.conf

Question 9

Which command would add the default gateway 192.168.1.1 to this interface?

Accepted Answer

ip route add default via 192.168.1.1 dev eth0. Option B is correct because the `ip route add default via 192.168.1.1 dev eth0` command explicitly specifies both the gateway address and the outgoing interface, which is necessary when multiple interfaces exist or when the kernel needs to resolve the next-hop without ambiguity. The `default` keyword is a shorthand for `0.0.0.0/0` in IPv4, and the `dev eth0` clause ensures the route is bound to the correct interface.

Answer

ip route add 0.0.0.0/0 via 192.168.1.1 dev eth0

Answer

route add default gw 192.168.1.1

Answer

ip route add default via 192.168.1.1

Question 10

A system administrator notices that the network bond interface bond0 is not operational. The bond is configured using mode 1 (active-backup). The physical interfaces eth0 and eth1 are both up but bond0 shows 'DOWN'. Which of the following is the most likely cause?

Accepted Answer

The physical interfaces must be set to the 'down' state before being added as slaves.. In Linux bonding, when adding physical interfaces as slaves to a bond in mode 1 (active-backup), the slave interfaces must be in the 'down' state before being enslaved. If they are already 'up', the bond may fail to recognize them correctly, leaving bond0 in a 'DOWN' state even though the physical links are up. This is because the bonding driver expects to take control of the interface's link state and will not properly manage a slave that is already administratively up.

Answer

The bond mode is set to an unsupported value.

Answer

The bonding module has not been loaded into the kernel.

Answer

The bond0 interface has not been assigned an IP address.

Question 11

A Linux router needs to forward DHCP broadcasts from clients on subnet 192.168.1.0/24 (eth0) to a DHCP server at 10.0.0.5. Which command starts a DHCP relay agent?

Accepted Answer

dhcrelay -i eth0 10.0.0.5. The correct command is `dhcrelay -i eth0 10.0.0.5`. This starts the DHCP relay agent (ISC DHCP relay) on interface eth0, listening for DHCP broadcast packets (UDP port 67) from clients on subnet 192.168.1.0/24 and forwarding them as unicast to the DHCP server at 10.0.0.5. The relay agent also relays the server's unicast replies back to the client, enabling DHCP service across subnets without a local DHCP server.

Answer

dhcpd -cf /etc/dhcp/dhcpd.conf

Answer

iptables -A INPUT -i eth0 -p udp --dport 67 -j REDIRECT

Answer

dnsmasq -i eth0

Question 12

Which THREE of the following are valid Linux bonding modes? (Choose three.)

Accepted Answer

balance-rr. Balance-rr (round-robin) is a valid Linux bonding mode that transmits packets in sequential order from the first available slave to the last, providing load balancing and fault tolerance. It is one of the seven standard bonding modes defined in the Linux kernel bonding driver.

Answer

link-aggregation

Answer

802.1ad

Question 13

A company requires link aggregation between a Linux server and a switch to increase throughput and provide redundancy. The switch supports only standard 802.3ad (LACP). Which bonding mode should be configured on the Linux server?

Accepted Answer

mode=4 (802.3ad). Option E is correct because mode=4 (802.3ad) implements the IEEE 802.3ad standard for Link Aggregation Control Protocol (LACP). This mode requires the switch to support LACP, which the scenario states, and provides both increased throughput through load balancing and redundancy through automatic failover if a link fails.

Answer

mode=2 (balance-xor)

Answer

mode=1 (active-backup)

Answer

mode=3 (broadcast)

Answer

mode=0 (balance-rr)

Question 14

A DNS server returns SERVFAIL for queries to a zone that is configured as a slave. The master server is reachable. What should the administrator check?

Accepted Answer

The zone transfer is allowed from the slave.. When a slave DNS server returns SERVFAIL for a zone it is configured to serve, but the master is reachable, the most common cause is that the master's zone transfer ACL does not include the slave's IP address. Without an explicit 'allow-transfer' directive (or equivalent) on the master permitting the slave, the master will refuse the zone transfer, leaving the slave with no valid zone data and thus returning SERVFAIL. This is a fundamental access control check in BIND and other DNS servers.

Answer

The serial number on the master is greater than on the slave.

Answer

The slave's allow-query includes the master.

Answer

The TSIG key is correct.

Question 15

An administrator needs to create a Linux bridge (br0) and add an Ethernet interface (eth1) to it for KVM virtual machine networking. Which set of commands accomplishes this task?

Accepted Answer

brctl addbr br0; brctl addif br0 eth1. Option C is correct because `brctl addbr br0` creates a new bridge interface named br0, and `brctl addif br0 eth1` adds the physical Ethernet interface eth1 as a port of that bridge. This is the standard sequence using the legacy bridge utilities to set up a bridge for KVM virtual machine networking, where eth1 becomes a member of br0, allowing VMs to share the physical network.

Answer

ifconfig br0 up; ifconfig eth1 up; brctl addbr br0; brctl addif br0 eth1

Answer

ip link add br0 type bridge; ip link set eth1 master br0

Answer

brctl addbr br0; bridge fdb add dev eth1 master br0