Monitoring Router Memory Utilization

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In a network, activities like adding a new device/IP address or changing the router configuration take a toll on memory consumption. Ultimately, when users in a corporate or other network experience slow network performance, network engineers telnet the routers to help identify root cause—possibly seeing messages such as:

%SYS-2-MALLOCFAIL: Memory allocation of XXXX bytes failed from…

To troubleshoot memory allocation issues, a solid understanding of different types of router memory goes a long way toward efficiently overseeing memory in both your network and routers. Keeping tabs on the utilization of all types of router memory on a network helps you avoid bottlenecks that can severely hamper network performance. If you have a Cisco® router, some of the common memory failure issues include:

  • Messages like Running low on memory; Unable to create EXEC – no memory or too many processes
  • Router running low on memory
  • Router hanging, or no response
  • Memory leak bug, or buffer leak bug
  • Large quantity of memory used for normal processes
  • Memory fragmentation problem or bug
  • Memory allocation failure at process = <interrupt level>
  • Insufficient shared memory for the interfaces

Unmonitored memory on core routers may lead to an unstable network or even disastrous network downtime. Having access to real-time memory stats of your core routers helps you troubleshoot faster.

To get the live memory statistics, you can telnet a specific router and run the appropriate command. For example, for a Cisco router, you would type: show processes memory. This displays the following type of information:


If you want to monitor all of your core routers, you may have to open multiple telnet sessions and run the command for each one. Instead of having this kind of raw stats for reviewing, it’s easier to review stats displayed in a visual format:

memory Monitor -graph

Network performance relies on your ability to rapidly identify and resolve memory bottlenecks. These often lead to slow network performance, slow or unresponsive applications, or application crashes. Therefore, using a visual format to view memory stats significantly lightens your workload.


Vaishnavi Vijayaram

Technical Communicator with a penchant for improving usability and user experience and provide usable content. Author of Learning Curve, part of the book - Negotiating Cultures: Case Studies in Intercultural Engineering and Technical Communication - published by IEEE Wiley (Institute of Electrical and Electronics Engineers, Incorporated) for Kansas State University, US.

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