Cisco CCNA
15 free questions with worked answers, and 149 more in the full bank.
Free questions
A junior technician notices collisions on an interface connected to a legacy hub. Which duplex setting is most likely causing this issue?
1 mark · Easy
After replacing a PC, the switchport logs show a continuous flapping of MAC addresses. What is the most probable reason for this behavior?
3 marks · Medium
An engineer analyzes a packet capture and observes ARP replies arriving without corresponding ARP requests. This behavior is indicative of what process or attack?
4 marks · Hard
Users complain of slow performance. An interface shows late collisions and CRC errors. What is the standard troubleshooting step for this symptom?
3 marks · Medium
A router needs to forward a packet but its ARP cache is empty for the destination IP on a directly connected subnet. What does the router do next?
1 mark · Easy
A router has three routes to 10.1.1.0/24: an OSPF route, an EIGRP route, and a Static route. Which route will be installed in the routing table?
1 mark · Easy
A packet is destined for 192.168.1.130. The routing table has 192.168.1.0/24 (AD 110) and 192.168.1.128/26 (AD 120). Which path does the router choose?
3 marks · Medium
A technician configures a floating static route as a backup to an EIGRP learned route for branch office connectivity. What is the necessary configuration step?
4 marks · Hard
Looking at the `show ip route` output, you see a route marked with a "D". What routing protocol generated this entry?
3 marks · Medium
You need to route traffic to the internet but do not have a specific route in the routing table. What kind of route should be configured?
1 mark · Easy
An admin notices a routing loop forming between three routers running RIPv2. Which mechanism prevents routing loops by not advertising a route back on the interface it was learned from?
3 marks · Medium
A multi-access OSPF network needs to elect a DR and BDR. Which router attribute is evaluated first to determine the DR?
1 mark · Easy
Two OSPF routers are connected over a point-to-point link. One router is stuck in the EXSTART state. What is the most likely cause of this issue?
3 marks · Medium
A network architect is designing a multi-area OSPF network. What is the strict requirement regarding Area 0?
4 marks · Hard
A technician is analyzing OSPF LSAs. Which LSA type is used by an ABR to advertise routes between different areas?
3 marks · Medium
More Cisco CCNA questions (page 1 of 3)
Answers and explanations are in the full bank.
- A router receives OSPF Hello packets from a new neighbor. Which OSPF state indicates the router has seen its own Router ID in the neighbor’s Hello packet? · 1 mark
- An engineer needs to prevent a specific router from ever becoming the DR on a broadcast segment. What configuration command achieves this? · 4 marks
- A small office uses a router-on-a-stick topology. Which protocol must be configured on the router subinterfaces to tag the traffic for different VLANs? · 1 mark
- A switch logs a `%CDP-4-NATIVE_VLAN_MISMATCH` message. What issue will this configuration error cause on the network? · 3 marks
- An admin configured an SVI (Switch Virtual Interface) on a Layer 3 switch for VLAN 10, but the interface shows up/down. What is the minimum requirement for an SVI to be up/up? · 3 marks
- To enable inter-VLAN routing on a Cisco Layer 3 switch, which global configuration command is required? · 1 mark
- A router-on-a-stick subinterface is configured with `encapsulation dot1Q 20 native`. What does the "native" keyword accomplish here? · 4 marks
- When a newly powered-on switch begins the root bridge election process, what default priority value is used in its Bridge ID? · 1 mark
- Two switches have the same bridge priority. Which attribute is used as the tiebreaker to elect the STP Root Bridge? · 3 marks
- In standard 802.1D Spanning Tree, an interface transitions from Listening to Learning state. What is the port doing during the Learning state? · 3 marks
- An administrator wants to speed up the convergence of Spanning Tree by using RSTP (802.1w). Which two legacy states are combined into the RSTP Discarding state? · 4 marks
- To prevent a PC connected to an access port from causing STP topology changes, which feature should be enabled on the interface? · 1 mark
- A junior admin needs to block a specific host IP from reaching any network. They decide to use a standard ACL. Which number range should they use? · 1 mark
- What wildcard mask is used to precisely match an entire /24 subnet (e.g., 192.168.1.0/24) in an ACL? · 3 marks
- An extended ACL is created to deny HTTP traffic from a specific subnet to a server. Based on Cisco best practices, where should this ACL be applied? · 4 marks
- An admin configured `access-list 10 permit 192.168.1.0 0.0.0.255` and applied it in on an interface. Pings to the router from 10.1.1.5 are failing. Why? · 3 marks
- Which keyword can be used in place of the wildcard mask `0.0.0.0` in an IPv4 ACL to match a single IP address? · 1 mark
- A small business uses PAT to allow 50 employees to access the internet using a single public IP address. What does PAT use to track the different sessions? · 1 mark
- When examining `show ip nat translations`, you see an IP address of 10.1.1.55 on the internal network. What NAT term defines this private IP address? · 3 marks
- A public IP address (203.0.113.5) assigned to your router's WAN interface is used to translate internal traffic. In NAT terminology, what is this address called? · 3 marks
- A network engineer needs to host a web server internally that is accessible from the internet. Which type of NAT is required for this configuration? · 4 marks
- Which router interface configuration command defines the interface connected to the ISP as the NAT external interface? · 1 mark
- Instead of using ARP, how do IPv6 hosts resolve an IPv6 address to a MAC address on the local network? · 3 marks
- An engineer configures an IPv6 interface. They notice an address automatically generated starting with `FE80::`. What kind of address is this? · 1 mark
- A router is using EUI-64 to generate an IPv6 interface ID. The MAC address is `0011.2233.4455`. What value is inserted in the middle of the MAC to create the 64-bit ID? · 4 marks
- An IPv6 host needs to find the default gateway automatically. Which ICMPv6 message does the router send periodically (or in response) to provide network prefix and gateway info? · 3 marks
- What is the IPv6 equivalent of the IPv4 broadcast address for sending packets to all nodes on the local link? · 1 mark
- A branch office router uses PPPoE to connect to the ISP. Which phase is responsible for user authentication using PAP or CHAP? · 3 marks
- Which WAN technology uses labels attached to packets to make fast forwarding decisions in a provider backbone? · 1 mark
- An admin configures a GRE tunnel over the internet between two sites. Which protocol is typically run *inside* the GRE tunnel to provide encryption, since GRE is cleartext? · 3 marks
- An enterprise wants to establish dynamic, on-demand IPsec tunnels directly between spoke sites using a hub router for control plane mapping. Which Cisco technology achieves this? · 4 marks
- When designing a modern enterprise WAN, which technology abstracts the physical hardware and uses centralized controllers to route traffic securely over any transport (MPLS, LTE, Internet)? · 1 mark
- An engineer runs `show cdp neighbors`. What layer does Cisco Discovery Protocol operate at to find directly connected devices? · 1 mark
- A security team mandates that network monitoring traffic must be authenticated and encrypted. Which SNMP version is required? · 3 marks
- A router generates a syslog message with a severity level of 0. What does this severity level indicate? · 1 mark
- An admin configures NTP to synchronize router clocks. Why is accurate time crucial for network management systems? · 3 marks
- What is the open-standard alternative to CDP for discovering directly connected multi-vendor network devices? · 4 marks
- Which data serialization format is commonly used by REST APIs and relies heavily on key-value pairs wrapped in curly braces {}? · 3 marks
- A DevOps engineer is using a configuration management tool that pushes configurations using YAML playbooks via SSH without installing an agent. Which tool is this? · 4 marks
- In Cisco DNA Center, which plane is centralized onto the controller, removing it from the individual physical routers and switches? · 1 mark
- A script is written to retrieve device inventory using a REST API. Which HTTP method is primarily used to request this data? · 3 marks
- A switch port is configured with port security. A violation occurs, but the port remains forwarding. Instead, it drops offending MAC traffic and increments the security violation counter. What violation mode is set? · 3 marks
- Which security feature creates a binding table of IP-to-MAC addresses by inspecting DHCP traffic to prevent rogue DHCP servers and spoofing? · 1 mark
- Dynamic ARP Inspection (DAI) is configured on a switch. For DAI to validate ARP packets properly, which database does it primarily rely on for non-static configurations? · 4 marks
- An admin configures `switchport port-security violation shutdown`. When a rogue device connects, what state does the switchport transition into? · 3 marks
- Which OSI layer is responsible for logical addressing and routing? · 1 mark
- A PC receives a frame. What field in the Ethernet header does it check to ensure the frame was not corrupted in transit? · 3 marks
- A router learns a route via OSPF and EBGP. The EBGP route has an AD of 20, OSPF is 110. Which protocol is installed in the routing table, assuming equal prefix lengths? · 4 marks
- What is the default OSPF Hello interval on an Ethernet broadcast network? · 1 mark
- You create a VLAN 50 on a switch but forget to assign any ports to it. You configure interface vlan 50 with an IP. What is the status of interface vlan 50? · 3 marks
- Which STP port role forwards traffic towards the Root Bridge? · 1 mark
- If you want to permit only hosts from 10.0.0.0 to 10.0.0.15, what wildcard mask is required? · 3 marks
- Which command is used to display currently active dynamic NAT mappings on a Cisco router? · 1 mark
- Which IPv6 prefix is designated for link-local multicast (e.g., used by routing protocols like OSPFv3 or EIGRP for IPv6)? · 4 marks
- What is the primary benefit of deploying an SD-WAN solution over a traditional leased-line WAN architecture? · 3 marks
- Which port does a syslog server listen on by default for unencrypted syslog messages? · 1 mark
- Which Southbound API protocol is frequently used by SDN controllers to modify forwarding tables directly on network hardware? · 3 marks
- A network engineer enables DHCP Snooping globally and on VLAN 10. However, clients are failing to get IP addresses from the legitimate server. What is the most likely missing step? · 4 marks
- A switch receives a frame with a destination MAC address of FF:FF:FF:FF:FF:FF. What does the switch do with this frame? · 3 marks
- When viewing `show ip route`, which character represents a route learned via a static configuration? · 1 mark