Cisco CCNA (200-301) - Enterprise Networking & IP Services Flashcards

Question 1

List the layers of the TCP/IP model and their primary functions.

Accepted Answer

The TCP/IP model consists of four layers:
1.  **Application Layer**: Provides network services to applications (e.g., HTTP, FTP, DNS).
2.  **Transport Layer**: Manages end-to-end communication and data segmentation (e.g., TCP, UDP).
3.  **Internet Layer**: Handles logical addressing and routing of packets across networks (e.g., IP, ICMP).
4.  **Network Access Layer** (or Link Layer): Manages physical addressing, media access, and data framing (e.g., Ethernet, Wi-Fi).

Question 2

How does the OSI model differ from the TCP/IP model?

Accepted Answer

The OSI model is a 7-layer conceptual model, providing a more detailed and theoretical framework for network communication. The TCP/IP model is a 4-layer practical model, more closely aligned with the actual protocols used on the internet. Key differences include the number of layers and how certain functions (like presentation/session) are integrated or omitted.

Question 3

What is the primary purpose of IP subnetting?

Accepted Answer

IP subnetting divides a larger network into smaller, more manageable subnetworks. Its primary purposes are to improve network efficiency by reducing broadcast domains, enhance security, and conserve IP addresses by allowing for more granular allocation within an organization.

Question 4

Explain Variable Length Subnet Masking (VLSM).

Accepted Answer

VLSM is a technique that allows network administrators to use different subnet masks for different subnets within the same IP network. This optimizes IP address usage by allocating only the necessary number of IP addresses to each subnet, preventing wasted addresses that would occur with fixed-length subnetting.

Question 5

What is Classless Inter-Domain Routing (CIDR)?

Accepted Answer

CIDR is a method for allocating IP addresses and routing IP packets. It replaces the old class-based IP addressing system (Class A, B, C) by allowing arbitrary-length prefixes (e.g., `/24`, `/27`) to define network boundaries. This improves routing efficiency and helps to slow the exhaustion of IPv4 addresses.

Question 6

What is the Cisco IOS command to configure a static route?

Accepted Answer

The command to configure a static route is `ip route [destination-network] [subnet-mask] [next-hop-ip | exit-interface] [administrative-distance]`.

Example: `ip route 192.168.2.0 255.255.255.0 10.0.0.1` (next-hop IP) or `ip route 192.168.3.0 255.255.255.0 GigabitEthernet0/1` (exit interface).

Question 7

When is a default route used, and what is its configuration command?

Accepted Answer

A default route is used when a router does not have a more specific route to a destination network. It acts as a 'gateway of last resort,' sending all unroutable traffic to a specified next-hop. It's commonly used to route traffic to the internet.

Cisco IOS command: `ip route 0.0.0.0 0.0.0.0 [next-hop-ip | exit-interface]`

Question 8

What are the advantages of dynamic routing protocols over static routing?

Accepted Answer

Dynamic routing protocols automatically discover and maintain routes, adapt to network topology changes (e.g., link failures), scale better in large networks, and simplify configuration compared to manually configured static routes. They exchange routing information with other routers to build their routing tables.

Question 9

Describe key features of OSPF (Open Shortest Path First).

Accepted Answer

OSPF is a link-state routing protocol that uses Dijkstra's algorithm to calculate the shortest path to destinations. Key features include:
*   **Link-State**: Routers exchange information about their directly connected links and their state.
*   **Hierarchical Design**: Supports areas to reduce routing table size and update traffic.
*   **Fast Convergence**: Quickly adapts to network changes.
*   **Classless**: Supports VLSM and CIDR.
*   **Cost Metric**: Uses a cost based on link bandwidth (lower cost is better).

Question 10

How is the OSPF Router ID determined?

Accepted Answer

The OSPF Router ID (RID) is a 32-bit value (like an IP address) that uniquely identifies an OSPF router. It's determined in this order:
1.  Manually configured using the `router-id` command.
2.  Highest IP address of any loopback interface.
3.  Highest IP address of any active physical interface.

Question 11

Provide a basic Cisco IOS configuration snippet to enable OSPF on an interface.

Accepted Answer

```cisco
router ospf 1
 network 192.168.1.0 0.0.0.255 area 0
interface GigabitEthernet0/0
 ip address 192.168.1.1 255.255.255.0
 no shutdown
```
(The `network` command under `router ospf` enables OSPF on interfaces whose IP addresses fall within the specified network and wildcard mask, assigning them to an area.)

Question 12

What is a VLAN and why is it used?

Accepted Answer

A VLAN (Virtual Local Area Network) is a logical grouping of network devices that allows them to communicate as if they were on the same physical LAN, regardless of their actual physical location. VLANs are used to segment broadcast domains, improve security, and enhance network performance and management.

Question 13

Explain the concept of VLAN trunking and the 802.1Q standard.

Accepted Answer

VLAN trunking allows multiple VLANs to traverse a single physical link between switches or between a switch and a router. The IEEE 802.1Q standard (dot1q) is the most common trunking protocol. It works by adding a 4-byte tag to Ethernet frames to identify which VLAN the frame belongs to, enabling switches to correctly forward traffic for different VLANs over the same trunk link.

Question 14

Provide Cisco IOS commands to create a VLAN and assign an access port to it.

Accepted Answer

```cisco
configure terminal
vlan 10
 name Sales
exit
interface GigabitEthernet0/1
 switchport mode access
 switchport access vlan 10
 no shutdown
end
```

Question 15

What problem does Spanning Tree Protocol (STP) solve?

Accepted Answer

STP (Spanning Tree Protocol) solves the problem of Layer 2 loops in switched networks. Loops occur when redundant paths exist, leading to broadcast storms, MAC address table instability, and multiple frame copies. STP intelligently blocks redundant paths to create a loop-free logical topology while still allowing for physical redundancy.

Question 16

How is the Root Bridge elected in STP?

Accepted Answer

The Root Bridge in an STP domain is the switch with the lowest Bridge ID (BID). The BID is a combination of a configurable bridge priority (default 32768) and the switch's MAC address. If priorities are equal, the switch with the lowest MAC address becomes the Root Bridge.

Question 17

List the primary port states in STP.

Accepted Answer

The primary port states in STP are:
*   **Blocking**: Does not forward frames, prevents loops, listens for BPDUs.
*   **Listening**: Listens for BPDUs, processes them, does not forward frames, learns MAC addresses.
*   **Learning**: Listens for BPDUs, learns MAC addresses, does not forward frames.
*   **Forwarding**: Forwards frames, learns MAC addresses, sends/receives BPDUs.
*   **Disabled**: Administratively shut down, not participating in STP.

Question 18

What is EtherChannel and what are its benefits?

Accepted Answer

EtherChannel (or link aggregation) bundles multiple physical Ethernet links into a single logical link. Its benefits include:
*   **Increased Bandwidth**: Combines the bandwidth of individual links.
*   **Load Balancing**: Distributes traffic across the bundled links.
*   **Redundancy**: If one link fails, traffic is automatically shifted to the remaining active links without interruption.

Question 19

Name and describe the two common EtherChannel negotiation protocols.

Accepted Answer

The two common EtherChannel negotiation protocols are:
1.  **PAgP (Port Aggregation Protocol)**: Cisco proprietary protocol. It helps automate the creation of EtherChannel links by exchanging PAgP packets between switches.
2.  **LACP (Link Aggregation Control Protocol)**: IEEE 802.3ad standard protocol. It also automates EtherChannel creation and is interoperable between different vendors' equipment.

Question 20

Differentiate between Static NAT, Dynamic NAT, and PAT (Port Address Translation).

Accepted Answer

*   **Static NAT**: A one-to-one, permanent mapping between a private IP address and a public IP address. Often used for servers that need to be accessible from the internet.
*   **Dynamic NAT**: A one-to-one, temporary mapping between a private IP address and a public IP address from a pool of available public addresses. The mapping is created when traffic is initiated from the inside network.
*   **PAT (Port Address Translation)**: Also known as NAT Overload, it maps multiple private IP addresses to a single public IP address by using different port numbers for each translation. This is the most common form of NAT, allowing many internal devices to share one public IP.

Question 21

Identify the core components of a basic Wireless LAN (WLAN).

Accepted Answer

The core components of a basic WLAN include:
*   **Wireless Access Point (AP)**: Connects wireless devices to the wired network.
*   **Wireless Clients**: Devices like laptops, smartphones, tablets with wireless adapters.
*   **SSID (Service Set Identifier)**: The name of the wireless network.
*   **WLAN Controller (WLC)**: (Optional, for larger networks) Centralized management for multiple APs.

Question 22

What are the recommended security standards for modern WLANs?

Accepted Answer

For modern WLANs, the recommended security standards are:
*   **WPA2 (Wi-Fi Protected Access 2)**: Uses AES encryption and 802.1X for authentication (Enterprise mode) or a Pre-Shared Key (PSK) (Personal mode). Still widely used.
*   **WPA3 (Wi-Fi Protected Access 3)**: The latest standard, offering enhanced security features like Simultaneous Authentication of Equals (SAE) for stronger password-based authentication, individualized data encryption in public networks, and improved cryptographic strength.

Question 23

What is the purpose of the `show ip interface brief` command in Cisco IOS?

Accepted Answer

The `show ip interface brief` command provides a concise summary of the status and configuration of all interfaces on a Cisco device. It displays the interface name, its IP address, its operational status (up/down), and the protocol status (up/down), making it useful for quickly checking interface connectivity and IP assignments.

Question 24

What is the purpose of the `show running-config` command in Cisco IOS?

Accepted Answer

The `show running-config` command displays the currently active configuration of a Cisco device. This configuration is stored in RAM and reflects all changes made since the last boot or save operation. It's essential for verifying configurations, troubleshooting, and understanding the device's current operational settings.

Cisco CCNA (200-301) - Enterprise Networking & IP Services

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