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Advanced Networking ConfigurationmediumMultiple ChoiceObjective-mapped

LPIC-2 Advanced Networking Configuration Practice Question

Exhibit

Refer to the exhibit.

# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 00:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff
3: eth0.10@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 00:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff
4: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 00:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff

# bridge vlan show
port    vlan ids
eth0     1 PVID Egress Untagged
br0      1 PVID Egress Untagged
eth0.10  10

The following output is displayed when running network configuration commands on a Linux system:

```

$ ip link show

... 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel master br0 state UP ... 3: eth0.10@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP ... 4: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP ...

$ brctl show

bridge name bridge id STP enabled interfaces br0 8000.000000000000 no eth0 ```

Based on this output, what is the configuration of the network interfaces?

⚠ Common exam trap

Test-takers frequently confuse VLAN subinterfaces with separate physical interfaces or assume eth0 is an access port, failing to recognize that a trunk port with a native VLAN and subinterfaces is the standard configuration for carrying multiple VLANs over a single link.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

eth0 is a VLAN trunk port with native VLAN 1; eth0.10 is a VLAN interface for VLAN 10; br0 is a bridge containing eth0.

In the typical Linux network configuration shown in these outputs, the physical interface eth0 is added to the bridge br0 (as seen with brctl show or ip link set master), making it a bridge port. The native VLAN on eth0 is VLAN 1, meaning untagged traffic on eth0 belongs to VLAN 1 and is bridged through br0. The VLAN subinterface eth0.10 is configured for VLAN 10 (e.g., using ip link add link eth0 name eth0.10 type vlan id 10), which handles tagged traffic for VLAN 10. This setup is consistent with a trunk port carrying multiple VLANs, where the native VLAN is untagged and other VLANs use subinterfaces.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • eth0 is directly connected to a bridge; eth0.10 is a separate physical interface; br0 uses VLAN tagging.

    Why it's wrong here

    eth0.10 is a VLAN subinterface, not physical.

  • eth0 is a VLAN ID 10 access port; eth0.10 is a separate link.

    Why it's wrong here

    eth0 has PVID 1, not 10.

  • eth0 is a member of VLAN 1 only; eth0.10 is a bridge port.

    Why it's wrong here

    eth0.10 is a VLAN subinterface, not a bridge port.

  • eth0 is a VLAN trunk port with native VLAN 1; eth0.10 is a VLAN interface for VLAN 10; br0 is a bridge containing eth0.

    Why this is correct

    Correct interpretation of the exhibit.

Visual reference

SW1 Root Bridge SW2 SW3 BLK DP DP RP RP STP blocks one link to prevent loops DP = Designated Port RP = Root Port BLK = Blocked

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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