KBI 311574 Issue Addressed: DeviceMagic Generates Inaccurate Bandwidth Usage For High Speed CISCO Devices


Argent Advanced Technology 5.1A-1707-F or below


Tuesday, 12 September 2017


CISCO devices might provide one or both sets of interface counters based on RFC1213 and RFC2233 respectively

The ifTable in RFC1213 is the traditional interface counters that almost all SNMP devices support

The ifTable defines 32-bit counters for inbound and outbound octets (ifInOctets/ifOutOctets) that are used for bandwidth calculation

The issue of 32-bit counters for high speed CISCO devices is that it wraps over too quickly

For example, a 10 Mbps stream of back-to-back, full-size packets causes ifInOctets to wrap in just over 57 minutes

At 100 Mbps, the minimum wrap time is 5.7 minutes, and at 1 Gbps, the minimum is 34 seconds

If the counter wraps more than once between Relator interval, the calculation is no longer valid

The ifXTable defined in RFC2233 implements 64-bit counters ifHCInOctets/ifHCOutOctets to address the issue

DeviceMagic in Argent Advanced Technology 5.1A-1707-F and earlier support RFC1213 only

As a result, the bandwidth calculation might not be accurate for high speed CISCO devices

The issue has been addressed in Argent Advanced Technology 5.1A-1707-G

Technical Background

DeviceMagic in Argent Advanced Technology 5.1A-1707-G is enhanced to support RFC2233


Even more important, the same device may or may not support 64-bit counters depending on the release of the operating system

An example of this extremely confusing situation is shown below:

  • Catalyst 2950 and 3550 – Support begins in Cisco IOS Software Release 12.1(11) EA1 since Cisco bug ID CSCdx67611 and Cisco bug ID CSCdw52807
  • Catalyst 2900XL and 3500XL – Support begins in Cisco IOS Software Release 12.0(5) WC3 since Cisco bug ID CSCds45300
  • Catalyst 5000/6000 ATM modules – Since Cisco IOS Software Release 12.0(14) W05 (20), refer to Cisco bug ID CSCds07238

Check your devices’ IOS level very carefully

Note: Cisco IOS Software does not support 64-bit counters for interface speeds of less than 20 Mbps

This means that 64-bit counters are not supported on 10 Mb Ethernet ports

Only 100 Mb Fast-Ethernet and other high speed ports support 64-bit counters


Upgrade to Argent Advanced Technology 5.1A-1707-G or above

In order to support 64-bit interface counters, the device must be configured to use SNMPv2c or SNMPv3 protocol, and explicitly set to use option RFC2233 or option ‘Dynamically Determined’ to allow Engine to determine