What are two characteristics of RAM on a Cisco device? (Choose two.)
- RAM is able to store multiple versions of IOS and configuration files.
- RAM is a component in Cisco switches but not in Cisco routers.
- The configuration that is actively running on the device is stored in RAM.
- The contents of RAM are lost during a power cycle.
- RAM provides nonvolatile storage.
The correct Answers:
- The configuration that is actively running on the device is stored in RAM.
- The contents of RAM are lost during a power cycle.
Detailed Explanation
Random Access Memory (RAM) is a fundamental component in Cisco devices, serving a critical role in maintaining the performance and functionality of routers, switches, and other networking equipment. RAM in these devices functions similarly to how it does in personal computers, providing temporary storage for data that is actively being used by the operating system and applications. However, Cisco devices have specialized uses for RAM that align with the requirements of real-time networking operations.
Two primary characteristics of RAM in Cisco devices are that it stores the configuration that is actively running on the device and that its contents are lost during a power cycle. Understanding these two characteristics is essential for managing and troubleshooting Cisco networking devices, as well as ensuring their continued operation.
1. The Configuration That is Actively Running on the Device is Stored in RAM
In Cisco devices, the actively running configuration is stored in RAM. This means that any real-time changes to the device’s configuration, such as modifications to IP addressing, routing protocols, access control lists (ACLs), or other network parameters, are maintained in RAM while the device is operational.
Running Configuration vs. Startup Configuration
Cisco devices have two main types of configurations: the running configuration and the startup configuration.
- Running Configuration: This is the active configuration that resides in RAM. Any changes made to the device while it is powered on (such as through the command-line interface) are immediately reflected in the running configuration. The running configuration is dynamic, meaning it can change at any moment based on administrator input or automated network processes.
- Startup Configuration: This is the configuration that is stored in non-volatile memory, specifically in NVRAM (Non-Volatile RAM). When a Cisco device boots up, it loads the startup configuration from NVRAM into RAM, turning it into the running configuration. This ensures that the device can resume its intended operation without manual reconfiguration each time it is rebooted.
The dynamic nature of the running configuration stored in RAM makes it critical for network administrators to periodically save their running configuration to the startup configuration, especially after making important changes. If an administrator fails to save the running configuration, any modifications made will be lost after a device reboot, since the startup configuration will be reloaded from NVRAM, not the running configuration stored in volatile RAM.
Saving the Running Configuration
To save the running configuration to the startup configuration in Cisco devices, network administrators typically use the following command:
copy running-config startup-config
This command copies the current configuration stored in RAM to NVRAM, ensuring that the configuration will persist across power cycles.
Impact of RAM on Device Performance
The speed and size of RAM in Cisco devices play a direct role in how quickly and efficiently the device can process network traffic. For example, large routing tables, complex ACLs, and intensive routing protocols like OSPF or EIGRP require significant amounts of RAM to operate effectively. As a result, devices with more RAM can handle larger networks and more complex configurations than those with limited RAM.
2. The Contents of RAM are Lost During a Power Cycle
Another critical characteristic of RAM on a Cisco device is that its contents are volatile, meaning they are lost whenever the device is powered off or undergoes a reboot. When the device loses power, all data stored in RAM—including the running configuration, routing tables, and other temporary data—disappears.
Volatility of RAM
The volatility of RAM means that it requires a constant power source to retain data. In contrast, non-volatile memory (such as NVRAM, flash memory, or hard drives) retains data even when the device is powered off. On Cisco devices, RAM is used to temporarily store the running configuration and other dynamic data, but this data will not survive a power loss or restart.
Effects of a Power Cycle
When a Cisco device undergoes a power cycle (a reboot or shutdown), the following process typically occurs:
- Power Loss: The device is powered down, and all data stored in RAM is erased. This includes the running configuration, ARP tables, routing tables, and any other data held in volatile memory.
- Power Up and Boot Process: Once the device is powered on again, it goes through a boot process. During this process, the device loads its operating system, typically from flash memory, which is a type of non-volatile storage.
- Loading the Startup Configuration: After the operating system is loaded, the device retrieves the startup configuration from NVRAM and loads it into RAM, turning it into the new running configuration.
- Rebuilding Dynamic Tables: Other dynamic data, such as routing tables or ARP tables, are rebuilt over time as the device interacts with other network devices.
This behavior is why it’s crucial to save the running configuration if you want changes to persist across reboots. Failure to do so means that the device will revert to the previous startup configuration stored in NVRAM, potentially causing network issues if critical changes are not preserved.
Real-World Example: Router or Switch Reboot
In the case of a Cisco router or switch, imagine that an administrator has modified the device’s IP addressing, set up routing protocols, and applied security configurations like ACLs. These changes are now part of the running configuration in RAM. However, if the device reboots unexpectedly—such as during a power outage or an intentional reboot by the administrator—the running configuration will be lost. Unless the administrator saved the running configuration to the startup configuration, the device will revert to its previous settings upon reboot.
This could lead to downtime, loss of connectivity, or security vulnerabilities, making it crucial for administrators to understand the volatile nature of RAM and the importance of saving configurations before any planned or unplanned reboot.
RAM in Cisco Routers and Switches
Both Cisco routers and Cisco switches contain RAM, and its functions are similar across both device types. In routers, RAM stores the routing tables, the running configuration, and any cache information related to routing protocols. For switches, RAM stores the MAC address table, the running configuration, and other operational data needed to forward traffic within the network.
The amount of RAM in Cisco devices often dictates the size of the routing tables or MAC address tables the device can handle. For example, larger enterprise-grade routers or switches with more RAM can handle more routes, more devices, and more traffic than smaller devices with limited RAM capacity.
Conclusion
In summary, RAM in Cisco devices plays a vital role in the operation of routers and switches. It stores the running configuration that governs the device’s real-time behavior, and it is volatile, meaning all of its contents are lost when the device undergoes a power cycle. These characteristics underscore the importance of managing configurations properly, ensuring that critical changes are saved to non-volatile memory before reboots. Understanding these aspects of RAM helps network administrators maintain stable, secure, and well-configured networks.