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- What is a subinterface in networking?
a. A logical subdivision of a physical network interface allowing multiple virtual interfaces on a single hardware port.
b. A type of physical cabling for connecting routers.
c. An interface used only for management traffic.
d. A redundant backup interface.
Answer: aomnisecu+1 - Which purpose do subinterfaces commonly serve on routers?
a. Allowing multiple VLANs to be routed over a single physical interface.
b. Increasing the physical speed of the port.
c. Acting as hardware firewalls by default.
d. Providing additional hardware for link aggregation.
Answer: anokia+1 - What is a typical configuration for subinterfaces when supporting VLANs?
a. Router-on-a-stick.
b. Hub-and-spoke.
c. Mesh topology.
d. Serial connection.
Answer: aomnisecu - Which encapsulation is most frequently used for VLANs on router subinterfaces?
a. 802.1Q.
b. PPP.
c. Frame Relay.
d. ATM.
Answer: aomnisecu - What is the naming convention for a subinterface on most routers?
a. PhysicalInterfaceName.SubinterfaceNumber (e.g., GigabitEthernet0/1.10).
b. PhysicalInterfaceName-SubinterfaceNumber.
c. SubinterfaceNumber/PhysicalInterfaceName.
d. Interface/SubinterfaceNumber.
Answer: anokia+1 - For which scenario would a network engineer create multiple subinterfaces on a single router interface?
a. Inter-VLAN routing.
b. Link aggregation.
c. OSPF area division.
d. Bandwidth throttling.
Answer: aomnisecu - When configuring a subinterface for a VLAN, what is typically assigned to the subinterface?
a. An IP address in the VLAN subnet and a VLAN ID.
b. Only a MAC address.
c. Only a serial number.
d. Only an IPv6 link-local address.
Answer: aomnisecu - Which command is used to create a subinterface on a Cisco router?
a. interface FastEthernet0/0.10
b. subinterface FastEthernet0/0.10
c. create sub-interface FastEthernet0/0.10
d. ip sub-interface FastEthernet0/0.10
Answer: aomnisecu - What must be true about the parent interface before any subinterface is active?
a. The parent interface must be administratively “up”.
b. The parent interface must have no IP address.
c. The parent interface must be in loopback mode.
d. The parent interface must be connected to a switch.
Answer: aomnisecu - In which types of solutions besides VLAN routing are subinterfaces used?
a. Non-Broadcast Multiple Access (NBMA) WAN solutions like frame relay or ATM.
b. Internet QoS only.
c. Only wireless networking.
d. Only point-to-point serial links.
Answer: aomnisecu - What happens if two subinterfaces are assigned the same VLAN ID on the same physical interface?
a. Traffic could be misrouted or discarded due to the configuration conflict.
b. Both will function for redundancy.
c. The router creates a failover group.
d. All traffic is load-balanced.
Answer: anokia - What is the maximum number of subinterfaces that can be created per parent interface with VLAN tagging on SR Linux?
a. 4096
b. 16
c. 2
d. 128
Answer: anokia - Which VLAN encapsulation protocol is the default for most Ethernet routers?
a. 802.1Q
b. ISL
c. Frame-Relay
d. PPPoE
Answer: anokia - What is the purpose of the “encapsulation dot1Q” command in subinterface configuration?
a. It specifies the VLAN ID the subinterface will handle.
b. It disables VLANs on the subinterface.
c. It sets an IPv6 address.
d. It specifies bandwidth limits.
Answer: aomnisecu - How are traffic flows kept separate on multiple subinterfaces of the same parent?
a. By assigning unique VLAN IDs or encapsulation parameters.
b. With unique MAC addresses only.
c. By physical cable separation.
d. By configuring trunk ports.
Answer: anokia - How does Inter-VLAN routing with subinterfaces improve network efficiency?
a. It reduces the physical hardware required by supporting multiple logical networks on one interface.
b. It increases broadcast domains.
c. It disables spanning-tree.
d. It reduces available bandwidth.
Answer: aomnisecu - What uniquely identifies each subinterface in its parent interface?
a. The subinterface index number.
b. The MAC address.
c. The routing table.
d. The subnet mask.
Answer: anokia - Which subinterface configuration step is mandatory for IPv4 packet routing?
a. Enabling the IPv4 address family and assigning an IP address to the subinterface.
b. Assigning a hostname.
c. Setting an MTU of 9000.
d. Assigning an IPv6 address.
Answer: anokia - What happens to packets with VLAN IDs that are unassigned in any subinterface on an interface with VLAN tagging enabled?
a. They are dropped or may be assigned to a “default” subinterface if configured.
b. They are routed via the management plane.
c. They generate spanning-tree recalculation.
d. They are broadcast on all interfaces.
Answer: anokia - What allows one physical Ethernet port to route traffic for multiple subnets simultaneously?
a. Configuring subinterfaces with unique VLAN IDs and IP addresses.
b. Changing the interface MTU only.
c. Setting up link aggregation.
d. Using a cross-over cable.
Answer: aomnisecu - How are IPv6 addresses configured on subinterfaces different from IPv4 addresses?
a. Each subinterface can have multiple IPv6 global unicast addresses.
b. IPv6 can only be configured on physical interfaces.
c. IPv6 must use link-local only by default.
d. Subinterfaces cannot be used for IPv6.
Answer: anokia - What is the Linux naming convention for subinterfaces?
a. Derived from the parent interface name, followed by a dot and a number (e.g., e2-1.0).
b. Parent interface suffixed by dash and index (e.g., eth0-1).
c. Subinterface_first (e.g., subif_eth0_1).
d. Only plain numbers (e.g., 1, 2, 3).
Answer: anokia - Which type of subinterface is required for routing IPv4 traffic between VLANs?
a. Routed subinterface.
b. Bridged subinterface.
c. Management subinterface.
d. Loopback subinterface.
Answer: anokia - What does the “no shutdown” command do when configuring a parent interface for subinterfaces?
a. Brings the parent physical interface up from Administrative down state.
b. Sets the interface as an access port.
c. Assigns an IP address.
d. Changes the interface name.
Answer: aomnisecu - In Cisco IOS, what range can subinterface numbers have?
a. 0 – 4294967295
b. 0 – 16
c. 0 – 255
d. 0 – 4095
Answer: aomnisecu - Which layer of the OSI model do subinterfaces primarily operate at?
a. Layer 2 and Layer 3.
b. Layer 1 only.
c. Layer 7.
d. Layer 4 only.
Answer: anokia+1 - What is a bridged subinterface used for?
a. For switching (not routing) traffic based on VLAN assignments.
b. For IP routing only.
c. For spanning-tree priorities.
d. For SNMP management only.
Answer: anokia - What must match for incoming VLAN-tagged frames to be assigned to a subinterface?
a. The encapsulation VLAN ID configured on the subinterface.
b. The MAC address of the frame.
c. The source IP address.
d. The parent interface’s speed.
Answer: aomnisecu+1 - What is the default TPID value for Dot1q VLAN tags?
a. 0x8100
b. 0x88A8
c. 0x9100
d. 0x8000
Answer: anokia - On a router, how many IPv4 addresses can be configured on a single subinterface?
a. Up to 64, including primary and secondary.
b. Only 1.
c. Up to 16.
d. Any number, no limit.
Answer: anokia - What must be done to move a subinterface from one network-instance to another?
a. Disassociate it from the first network-instance before associating it with the second.
b. Delete and recreate the parent interface.
c. Only change the VLAN tag.
d. No special steps are required.
Answer: anokia - Which configuration would you use for routing multiple VLANs over a WAN link?
a. Subinterfaces with 802.1Q encapsulation.
b. Spanning-tree on each VLAN.
c. Separate physical routers.
d. Add access-lists to each interface.
Answer: aomnisecu - What describes an “unnumbered” subinterface in IPv4?
a. It borrows the IPv4 address from another interface rather than having its own.
b. It lacks a MAC address.
c. It can’t forward packets.
d. It only handles link-local traffic.
Answer: anokia - What is the benefit of unnumbered subinterfaces?
a. Simplifies network design by reducing address requirements.
b. Prevents OSPF adjacency.
c. Increases router CPU usage.
d. Reduces interface MTU.
Answer: anokia - Which subinterface type is used when connecting to a mac-vrf network instance for switching VLANs?
a. Bridged subinterface.
b. Routed subinterface.
c. System subinterface.
d. Loopback subinterface.
Answer: anokia - What encapsulation type allows a subinterface to match any VLAN tag?
a. vlan-id any
b. vlan-id 4095
c. vlan-id none
d. vlan-id 0
Answer: anokia - What does the following configuration do: “interface ethernet-2/1.2 { vlan { encap { single-tagged { vlan-id 101 } } } }”?
a. Assigns VLAN 101 to subinterface 2 of ethernet-2/1.
b. Sets up a trunk for all VLANs.
c. Creates a loopback interface.
d. Adds IPv6 capabilities.
Answer: anokia - What is the result of configuring multiple subinterfaces with single-tagged VLAN ranges on the same interface?
a. Allows each subinterface to handle distinct VLAN IDs or ranges.
b. Collapses all VLANs onto one subinterface.
c. Disables VLAN support.
d. Forces all subinterfaces to act as untagged.
Answer: anokia - In what scenario would a default subinterface be used?
a. To capture untagged and unconfigured VLAN-tagged frames.
b. For OSPF area assignments.
c. For Interface aggregation exclusively.
d. For PPPoE traffic only.
Answer: anokia - What is the maximum number of global unicast IPv6 addresses per routed subinterface on SR Linux?
a. 16
b. 1
c. 8
d. 64
Answer: anokia - What is the default behavior of a router if untagged traffic arrives on an interface configured only with VLAN-tagged subinterfaces?
a. The traffic is dropped unless an untagged subinterface is configured.
b. It is assigned a random VLAN tag.
c. It is passed to all subinterfaces.
d. It is assigned to VLAN 1 by default.
Answer: anokia - What must you configure to allow IPv6 routing on a subinterface?
a. Enable the IPv6 address family and assign a global unicast address.
b. Set up IPv4 static routes.
c. Assign multiple MAC addresses.
d. Enable OSPFv2 only.
Answer: anokia - Which command in SR Linux displays the VLAN configuration for subinterfaces?
a. show interface detail
b. vlan show detail
c. show vlan-all
d. show vlan-state
Answer: anokia - What happens when a subinterface is administratively disabled?
a. The subinterface cannot send or receive packets.
b. It becomes a DHCP relay.
c. It only handles local traffic.
d. It is assigned to the default VLAN.
Answer: anokia - How can you uniquely identify each subinterface in Linux?
a. By their Linux name, such as e2-1.0.
b. Only by switch MAC address.
c. By physical location in the data center.
d. By VLAN ID only.
Answer: anokia - What field in the show interface command indicates the TPID for VLAN tagging?
a. VLAN TPID
b. VLAN MAC
c. VLAN Switch
d. Port Type
Answer: anokia - Can subinterfaces be assigned to different network-instances at the same time?
a. No, a subinterface can only be associated with one network-instance at a time.
b. Yes, for redundancy.
c. Only in Layer 2 mode.
d. Yes, with trunking enabled.
Answer: anokia - What does configuring “vlan encap untagged” on a subinterface do?
a. It allows untagged frames to be accepted on a tagged physical interface.
b. It disables VLAN tagging.
c. It converts all traffic to tagged mode.
d. It restricts all traffic to VLAN 1.
Answer: anokia - What could cause an operationally down state on a subinterface?
a. If the parent physical interface or required address family is not enabled.
b. If too many IPv4 addresses are configured.
c. If the subinterface index is above 100.
d. If OSPF is not running.
Answer: aomnisecu+1 - What is the effect of “vlan-id any” in subinterface configuration?
a. It matches and accepts traffic for any VLAN that is not explicitly configured on another subinterface.
b. It disables the subinterface.
c. It only accepts VLAN 1 traffic.
d. It sets the subinterface as default gateway.
Answer: anokia
