What is Connection Utilization Coding and why should you enable it?

CUC-Color-and-linewidthConnection Utilization Coding (CUC) is the functionality that applies a color and/or width to a network connection line, according to its utilization level. The value displayed is the highest measured utilization of both endpoints of a connection, regardless of the of the traffic direction (upload/download).

CUC helps in detecting potential problem spots, congestion or traffic anomalies!

How to enable Connection Utilization Coding

CUC is enabled by default and requires no configuration. However, CUC works by combining device MAC addresses and port forwarding information collected from various SNMP MIBs and thus only works if the following conditions are met:

  1. You’re using layer-II or layer-III devices (bridges, switches or routers) that support the dot1dTpFdbTable group ( of the Bridge MIB (rfc1493).
  2. SNMP is enabled and working properly on those devices.
  3. The connected devices (Servers, PCs, Printers etc) support the ipAddrTable group of the IP MIB (rfc1213).
  4. SNMP is also setup, enabled and working correctly on those devices.
  5. Network topology maps have been set up accurately and correctly!

If not all conditions are met, CUC will not be able to determine a connection’s utilization and considers the connection “unmanaged”. In this case, the line color is set to gray and the width to 3px. To keep the load of SNMP traffic on a network as low as possible while collecting the data needed for CUC, it usually takes 10-20 minutes before CUC presents the first color coded lines! The screenshot above shows the backbone of a high-capacity network with CUC in action.

Coding options

CUC offers 4 coding options that can be chosen from on the Administration | Various system settings page. The options all affect the way how utilization coding is displayed. The screenshots below show the available options and what they look like.

Connection Utilization Coding dusplay options

The available CUC options. The default is “Color coding”.

No CUC coding

Option 1 – No coding.


Option 2 – Only the line-width varies according to the utilization of the connection. The utilization of the connection from Calcium to Switch01 could not be determined. Calcium has the “down” status!


Option 3 (default) – Color coding. The connection between Calcium and Switch01 is “unmanaged”. Device Gold is transferring a file to Silver and also to Platinum!


Option 4 – Utilization coding through color and line-width!


If the traffic on a network is very low, let’s say less than 5% (it’s beyond working hours or your network is over-dimensioned) and you still want to get an indication of where the most traffic flowing through your network is, you can set a scale factor.

The scale factor ranges from 1 to 10 where scale factor 1 effectively means “No scaling”. When scaling is applied, each Map page will get a notification in the bottom-right corner.


This screenshot shows the same network as the screenshots above but now with a fixed scaling factor of 2. Note that the labels now show the letter “s” (scaled) appended to the utilization!

Finally, there’s also the option Relative which means that all connections are color-coded relative to the connection with the highest utilization. The screenshot below shows an example.


Device Gold is sending files to the devices Silver and to Platinum at the same time at a bandwidth rate of 100%. 69% of this bandwidth goes to Silver, 31% goes to Platinum! Note that the labels now show the letter “r” (relative) appended to the utilization!

Custom color mapping

Besides the scale factor you can also define your own color map by using the integrated color picker. Just click an existing color, select a new one and save your settings!

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